The Boy Genius claims, based on info from a source who's proven reliable before, that we haven't gotten an iPhone OS update recently (oh, hai still missing iPhone 3.2!) because:

there’s too much tablet-related code/references in the OS and Apple obviously didn’t want that to leak.

He's also heard that multitouch gestures for the iTablet/iSlate are "out of control", it's got a super-fast ARM processor that runs the iPhone OS kernel, is model K48AP, and is pretty much an "iPhone on steroids".

If this pans out, being so closely linked to the iPhone will no doubt disappoint Mac OS X tablet enthusiasts, but benefit the iPhone in terms of leveraged development and shared features.

Either way, we can still only expect it when we see it...