The earliest we'll see a Rev E MacBook Air is June, and more likely this fall. The guessing game will begin, however.
I'm surprised Apple kept the Core 2 Duo MacBook around. Maybe that will be quietly updated in the coming weeks along with the Mac Mini. Whatever those get upgraded to will give us a hint as to what the next MacBook Air will have. I doubt very seriously we'll get a Core i5 in the next MacBook Air (Core i3 is more likely), but if the MacBook or Mini get them I'll change my view on that. Thunderbolt is a possibility, though.