My guess:

Killer phone hardware (improved speed, battery, display, cameras)

Nice iPhone OS tweaks (better workflow via faux multitasking, a background iChat client, some really nifty iPad features)

Some sort of content partnerships on the iTunes / AppleTV side

...and that's it.

Still AT&T only, still tied to iTunes, still locked down platform and app store, still no flash.

And I will be disappointed. But holding off to buy a new phone until I see what he's got!