I'm getting the newest 3gen since I'm updating from an ipad1 and I thought it would tide me over better through the 4-5th gens rather then an ipad2 and wanting what all the newest ones have. I think if I already had an iPad two I'd wait for the next one (like every other upgrade?)
There will always be a newer, better more "OMG SOME AWESOME" piece of technology in six months anyways.
The question is, can you resist the temptation?!
Also, when trading in or selling, the 3gen will be worth more to swap with then the 2gen. But if you have the cash to out right buy one, or a person who would pay top dollar, then I suppose that wouldn't matter as much.