Expected: A5 CPU, higher spec CMOS camera. Let's hope it has larger screen, longer battery life, Bluetooth 4, faster 801n. Or maybe NFC chip for wallet type application? I suspect Square people already has some insight. Its more than iPhone 5 event: iOS 5, iCloud, new iPod touch, new iPod refreshes or even new Apple TV. Updated: Not sure why its voted down. I don't work for Apple.
I think there will be MacBook Pro bumps too. Although I hear the MBP redesign is now pushed back to 2012, unfortunately.
Refreshes have frequently gone out in the past without any sort of event and I'd guess that this would be the case this time.