Can't believe I'm just reading this for the first time, very awesome news!
As a side note, I bet it will be a disk based release. Poor comparison, but when Raw vs Smackdown 2009 released new characters ppl who didn't buy them had to go to the PS Store and DL a patch or the match wouldn't go thru when playing online. I don't see a SF4 expansion DLC with new supers, combo's, balancing, ultra's, and new characters playing well with an unpatched version of SF4. I think it'll be packaged as a new game like Capcom has always done (Street Fighter 2 - Super Street Fighter 2, all 3 Alphas, all 3 Street Fighter 3's, ect.)
I'm like you guys in that I'd rather see it as DLC with a cheaper price point, but I don't think Capcom will do that when there's an easier and more profitable path.