It'd be nice if it was a flying device, if it had robot legs and took pictures by itself.
Seriously let's stick with realist things to expect: better sensor in every aspect, big af update (something between 7d and 60d IMO), digic V, something surprising in video mode (even if I don't care), built-in flash transmitter, probably two card slots like d700 (or not), a re-designed body (more ergonomic, sorry the bg-e6 won't fit
), more customizable options in the menus.
PLEASE GOD I DON'T WANT AN ARTICULATING SCREEN (amen).
I don't think there will be much more than that, but "that" already makes it a great upgrade.