I’m only going to make one prediction for WWDC this year, and it’s one that probably won’t be verifiable for a bit of time. With that in mind, I’ll just leave this here.
I think iOS 7 is the OS that we’ll be able to look back on and say this is where it started to grow up. I think there will be multitasking changes, and inter-app communication, and settable default apps. This is in preparation for a day where we see the iPad take on bigger form factors, and be more usable.
I don’t think that OS X has a future where it merges with iOS, but I can see a 13” iPad on your desk. iOS is not currently fit to really do that, but with some attention it can get to the point where it does (almost?) everything that Mac can do, but simpler.