While home automation would be great, I think a good platform has already been implemented with HomeKit and now it's up to hardware manufacturers to begin integrating it. There's not a great deal more Apple can do apart from pushing it to more appliance manufacturers.
From a developer's point of view, I think most agree that it'd be nice to be able to build apps for the Watch which run natively without the need for an iPhone. I doubt we'll see that in June as it seems a bit early - maybe later in the Autumn with iOS 9.X and the 6S. I'd also like to see a better way of handling files on iOS. Not necessarily a full file system, but the system of not being able to open files unless you have a compatible app installed, no one area for files to go seems a bit silly. I think it was fine three or four years ago, but the iPhone has matured since then and it's plain to see that Apple think of it as more than a phone and an iPod now. iCloud Drive was a good start but you still can't access that outside of an app.
However, my biggest wish as a developer (and a consumer!) is access to Siri APIs for third party apps. Personally, Siri still hasn't gone past setting alarms and reminders for me. Imagine if you could use it to play Spotify, to buy something from Amazon, to control your TV and thermostat, to look something up on YouTube, to get sports results (I know Siri ostensibly does this already, but third party apps would let it get results from sports like rugby and lower-league football which it doesn't currently support), to check your balance on your current account, to get bus times and bus stop locations. The possibilities are endless, and it's one feature I think is criminally neglected by Apple.
iOS 9 would be a great time to introduce a revamped Siri, especially with one of the few visual changes rumoured to be a new Siri interface reminiscent of the Apple Watch.
