Uh.....none of those options sound really that great....or viable. Guilty Gear and Smash Bros are completely different engines and most likely wouldn't work without greatly altering one of the games engines/sprites (therefore the entire gameplay). DC is already being done by Midway with DC vs MK. And FF and DBZ are rather limited (and FF was already covered in house by SquareEnix and Dissida).
Frankly, I'd rather just see a Capcom vs SNK 3. When you think about it, the Capcom and SNK licenses are two of the biggest fighting licenses out there. And they have hardly touched on all the characters of either one. In fact, the previous titles mostly just used the 'popular' characters from both. They could go a lot more in depth and use a lot more obscure or technical characters such as Billy Kane, Hotaru, Fei Long, Strider, etc and make a game that really encompassed both sides strengths and variety.
Six upcoming games you should look into:
