Seven's a good number, IMO.
(I mean, we've got five in the promo art, and nobody here'd be completely happy if that was the whole team, would they?)
So we go
Talisman (I'm almost 100% sure on her)
Beta Ray Bill (who, as a Thor geek, I'm happy to see anywhere. I wanna see him smite that Clone)
U.S. Agent (I can see all kinds of fun with this ultra-nationalist jackass)
SOMEBODY in the Guardian Suit (and I really hope it isn't Mac)
Arachne/Spider-Woman/Random Chick I can;t be arsed to speculate on
And then an original cast member- Note, original cast, not original team. Maybe Heather plays Oracle for them. Or maybe an early Beta-Flighter makes an appearance. Whatever the case may be, we're going to get further old-school fun.
And for the seventh? I'd like to see some weird character nobody (myself included) really thinks about very often, given a chance to do something cool.