It's not bloody likely to hear a "Street Fighter 4" coming out... 2-D fighters are seemingly going the way of the dinosaur. The only 2-D fighter I can think of that's pretty popular is Melty Blood.
Yeah, those also...How well did KOF XI fare in Japan, btw?
^I've thought about getting MAME for arcade roms, mainly for some of the older fighting games I used to play, but I'd have to find myself a good arcade-style fighting stick.
If anyone is interested in learning about Super Turbo, David Sirlin made tutorial videos you can watch on his website here: http://sirlin.net/