I too believe it will feature a few "hub" cities (where everyone can interact with each other) then you split off in your groups and do instanced (private) missions. But until I hear who is actually involved with making this game, my expectations are low. Made lower by Bendis's involvement.

But being able to play a game set in the Marvel U, especially our own version of the Flight would be awesome.
But, it's a long ways away I'm sure. Typically MMO's can take 3-5 years to be developed then launched. I've been waiting on Star Wars The Old Republic I think for four years now.