I had the high-end 2010 13" MBA {2.13Ghz, 256GB Flash, 4GB of RAM}...it performed fine...no...great...for everyday computing but for $1,730 it was overpriced for its ability. The dated dual-core couldn't keep up when virtualizing. Mac's are overpriced, but I do like the hardware and I like OS X...at least as much, if not more, than Windows 7.
As to speculating about the 2012 MacBook Air. I'm thinking it may be some Core i5...but if its as much a jump in performance over the current model as the 2011 MacBook Pro's were over the 2010's then it would be a pretty slick machine.
I wouldn't trade my 2011 MacBook Pro for one though...I like this thing...even though its overpriced.