Well, we're a month away from WWDC, so it's the time for exciting speculation about what's to come. This year is looking to be the year of Mac OS X updates, most notably a UI refresh to align more with the iOS products. I'm not going to spend any time covering Mac OS, since I don't develop in that space. However, I think there's some big potential for what's coming for iOS.
There are a few major areas where I think Apple is going to do some cleanup/overhauling of their existing iOS offerings.
Maps updates - Extremely likely
Look for updates to maps that include things like transit directions, offline use, better user data collection, and possibly a slightly tweaked interface. Maps has been a big hurting point for Apple since it launched, and a great deal of the the iOS users I know have installed and exclusively use Google Maps.
GameCenter updates - Extremely likely
Some tech blogs are reporting the upcoming death of the Game Center app. I think this is more likely to be a shift away from Apple's past behavior of shipping phones with lots and lots of stock apps. I would expect to see some sort of App available on the App store that replaces any removed stock apps. There are two benefits to Apple for doing this: They can get updates to those apps faster with App store updates. Also, it will provide a cleaner experience for new users, who may be overwhelmed by the number of apps that Apple currently stocks on a device out of box. It wouldn't surprise me if Apple targets having only one screen's worth of Apps stocked on a device OOB.
If they don't remove the Game Center app, expect a visual overhaul. Today's implementation is confusing and visually different than the other experiences.
Passbook and "iHealth" - Unlikely
Apple is likely readying some updates to their existing Passbook app, and additionally preparing to introduce a Healthbook app to correspond with their upcoming iWatch. I expect these items to be introduced with products that enhance their features, such as the iWatch or an iPhone 6 with NFC.
UI updates - Moderately likely
The iOS7 visual update was drastic, and not well received by many in the design community originally. I expect they will make some minor tweaks to iconography, and possibly color uses. Expect the same overall visual impression, however. Some of the visual changes will come from a need to align with their new Mac OS X visual requirements as well.
Xcode & Developer APIs
Just a comment before I get into this. I'm seeing a trend where Apple makes developing apps easier and easier for non-developers on a yearly basis. Expect Xcode and the supporting APIs to be moving in a more user-friendly direction. Creating an app for iOS or even Mac OS is so much more accessible now than it was just 2-3 years ago.
TouchID framework - Moderately likely
TouchID will become very useful to developers when it's released. It has the potential to make our everyday login interactions quick and seamless. Additionally, I expect TouchID to connect with Mac OSX in some nifty ways, such as being able to login to your Mac using your iPhone's Touch ID sensor. Its a natural pairing in the effort to kill the password. Eventually this will lead into a mobile payments solution, which I don't expect to be announced until the release of the iPhone 6/iWatch.
SpriteKit updates - Extremely likely
Given how new SpriteKit is, I expect to see some improvements, enhancements, additions. Less likely - I would be especially impressed if Apple managed to build an interface builder equivalent for SpriteKit so views didn't have to be generated in code every time. That would really start a renaissance in rookie iOS developer game creation.
Core Data improvements - Moderately likely
Core Data is in a surprisingly good place right now, but I feel it needs some minor tweaks to get it useful to the level that unseasoned developers can get rolling with it. First of all, it takes a ton of code to get Core Data up and running on your app. For something that's required to save information to the phone, this is surprising to me. I'd love to see some strides at making Core Data a 2-3 code line add-in. Secondly, I've read a lot of reports about iCloud data synchronization being a bag of hurt, so definitely expect improvements there.
Interface Builder - Extremely likely
It's pretty clear that the next iPhone will have a 4.7" screen, necessitating developers to create experiences that work on a multitude of screen sizes. Currently, developers only had to worry about changes in one screen dimension, which is especially easy for most developers to deal with given the strong preference to use UIScrollViews and UITableViews anyway. Wider screens are going to cause some issues, as a lot of interface elements have been sized according to aesthetically pleasing amounts of whitespace. Multi-size layouts will wreck havoc on this.
Thankfully Apple already has the pieces in place to solve this problem: Auto-layout. Unfortunately Interface Builder slows way down with Auto-layout if you start to introduce several objects in a ViewController. So look for improvements in speed at the very least.
Additionally, I think Apple will make some visual overhauls to Interface builder that let designers zoom in closer than currently allowed, and more easily see how items are going to scale with different view sizes.
iBeacon - Extremely likely
This is an item that hasn't been widely speculated about, but I feel confident there will be significant updates to.
There are two problems with iBeacon technology currently. The first problem is that it's aimed entirely at commercial uses... ie. push advertising. Granted, its the most relevant kind of advertising to date (things that are in front of you), but Apple has to know that technologies focused entirely on making people buy things aren't going to gain the momentum they need to stay alive. Apple needs to make this technology available to developers in non-advertising focused scenarios. That means there will need to be some changes to the discovery process. Currently you can't get a list of nearby iBeacons unless you know their UUID. I expect that to stay the same for retail use-case iBeacons, but I do expect some sort of public discovery method to be created for non advertising uses.
Second problem is that users have to download the app for a specific iBeacon's business to interact with the beacons. This isn't a big problem for massive corporations such as Target. If they introduced iBeacons in Target, the thousands of users who use their Target app or Cartwheel app could get those notifications. However, for a small business to implement iBeacon technology, they would only be able to reach the minor number of people who happened to download their app. Apple could solve this with some sort of push notification service. This would be a very complicated problem to solve correctly, as the advertising could get out of hand. However, the problem is very real, and needs a solution.
The wish list - Extremely unlikely
There are a couple other things I would love to see added that I don't think have a snowman's chance in hell of happening.
• Airplay from iOS to an OS X window
• Wireless App Testing in Xcode - No lightning cable required!
• Siri API - allowing 3rd party apps to introduce Siri commands.
WWDC hasn't been the hardware spectacle it used to be lately. However, there's a minor potential for some hardware items to be announced.
iBeacon Keyring - Somewhat unlikely
As a part of the previously mentioned effort of getting iBeacon actually useful for users, I can see Apple creating an iBeacon powered keyring that enables an app to detect how far away your car keys are. Also integrated into this app could be a way to make nearby user's phones sound out an alert (a faster version of Find my iPhone). There are a few kickstarter projects that use similar technology, but I think Apple is in a core place to be able to provide this for super-duper cheap, and give iBeacon the boost it needs to becoming a world class standard. Expect a minimalist design, with a battery that lasts 2-3 years. Bonus kudos if it includes a method to reverse find your iPhone from the keyring.
OS X fingerprint reader - Unlikely
I actually find this one more and more unlikely the more I think about it, but I could see Apple trying to have one for one hardware equivalents to iOS products for their Mac line. They already do this to some extent with the Magic Trackpad, offering touch interactions for your Mac. The next logical step will be incorporating technology that allows secure e-commerce transactions.
Retina Cinema Display - Somewhat unlikely
The cinema display is way overdue for an update, and I think WWDC could be the place we see it. With the Mac Pros being touted as 4K compatible, I don't see why Apple isn't offering a top of the line 27"-30" display. Maybe they're holding off because they don't want Retina Macbook Pro owners lusting over something that would give them bad performance if they were to hook it up?
Prepare for mostly Mac OS news, but expect a good 45 mins of the keynote to be spent on updates to iOS. If you think I've missed something big, let me know on Twitter @adammillers or in the comments below.