If the next iPhone is just fine tuning (and this is my opinion too) then maybe the keynote will have even more of the time devoted to app showcases. If the CPU does get a worthwhile boost then maybe they'll want to showcase that as much as possible.Someone mentioned Steve Job's Keynote for next year's iPhone (perhaps 5, but more likely 4s or something).
When you think about what would be keynote-worthy, and possible in 8 months, it's not going to be an newly redesigned phone. It will have to be limited to software updates, maybe a new processor, 8 megpixel camera and a redesigned external antenna.
Also, if the next phone has NFC (Near Field communication) capabilities built in then they could spend some time talking up the sort of capabilities that NFC could bring. Given that I suspect that Apple would like to get a cut of the revenue stream for some possible NFC services then it's in their interests to try and accelerate the uptake of these services.
- Julian