Nuh uh, Guilty Gear has to stay a 2D fighter. It's the only way it can be good.
And it's way too early for BB to be the new poster child. It just friggin came out, man. It's popular, but it's not that popular yet. It's still very niche.
BB is what they've been working on for the last 5 years (at the least), while the various GGXX updates during that time were serving to give them some nice capital all the while. They're DAMN sure going to make BB the new flagship, for all that work and money they've poured into it. Expect BB to be rocking it by itself in that avenue for quite a while.
Besides, like I said, it's highly improbable to expect ASW to market two different 2D HD fighting games within the same time frame. They're not going to want to market two similar games against each other, one being even MORE niche than the other. And that's actually GG, right there. Because, for all that it's more well known, only the hardcore have the stomach for its gameplay; BB is much more "casual-friendly", for that reason.
So, really, there's only 3 ways that are probably ideal at this time. Either
a) GG goes 3D with the same 2D style game play (largely) intact. Could be possible, given Battle Fantasia proving that ASW at least is capable of such a thing. It'd be cheaper/easier to construct, and the pressure would be eased a bit on two similar games, from the same company, being marketed against one another.
b) Moar Overture. However, giving that the original 360 game didn't exactly ring any bells (and didn't get a PS3 port), it makes me doubt we'll get where that came from. It could be something entirely different (all over again).
c) Something else completely unexpected (probably 3D). Ishiwatari is certainly capable of such. And if it's going to be predominantly console-only affair, this is his big chance to do as such.