128 or 256GB versions wouldn't be practical... not with the current pricing scheme. You're paying more than you would for a laptop/ultrabook then. Better compression of files (so these app sizes decrease a bit), increased Cloud storage and usability would be nice.
As far as the device itself, damn. We're still in the original "30-day, take it back if you don't like it" window. I don't see much in the way of hardware revisions, actually. It will probably lose the added bulk it picked up going from the 2 to the 3. Hopefully they improve the Facetime camera and give the CPU a healthy performance bump. Oh, and do something with the speaker. Move it, refocus it, give us 2... something.
Other than that, most of the big changes will probably be software related, and have more to do with iOS 6 and desktop/mobile integration. (Think along the lines of what Windows 8 is proposing) One thing I'm pretty sure we WON'T see is haptic tactile feedback. People got unjustifiably excited about that around a month ago... not happening. Not practical.