If your current RevA MBA does what you need it to do... why are you thinking about upgrading?
There's two schools of thought to keeping happy in the tech world, IMHO:
a) "Latest and Greatest" -- this is a super-techie who needs to have the newest tech available all the time, and probably only goes 6-8 months with the same computer before getting a new one.
This person will never be disappointed 'cause they're always upgrade to new stuff, and they're either rich, or they can get a decent amount of $$ for their "old" gear to offset their constant upgrade cycle.
b) "Upgrade when you need to" -- this person keeps a computer for 2, 3, 4 years or until it no longer functions for what it needs to do for them.
This person will never be disappointed 'cause they wait till they *need* a new computer and buy it then, never looking over their shoulder at whether they should wait for the next "latest and greatest" 'cause they bought when the absolutely needed to, vs. on a whim.
If you're not in group a or group b, I'd say there's always a chance you're gonna be disappointed with your purchase - either waiting for the "latest and greatest" forever... or buying a new one but then constantly agonizing over it till the next new one comes out and then wondering why you didn't wait.
Bottom line: If you want it, and you can afford it, and the 2010-MBA does what you like and need - get it.
The RevE will be out sometime on 2011 and it'll be better, but no-one has a crystal ball as to when that'll be (though some, like me, have hedged bets on Summer 2011).