My top two from those screen shots not currently released would be:
1) Squirrel Girl
2) Grey Hulk (Mr. Fixit)
I agree with others that FF Invisible Woman and Mystique are highly probable as well. Mystique is a slam dunk because you would think they'd have to do very little work to get her up and running as a playable character. I thought it was very odd when Invisible Woman was removed from the store, leaving an incomplete Fantastic Four available (we don't even have a Fantastic Four version of She-Hulk to replace Sue with!) so given the Doom voice interaction and the lack of Invisible Woman currently available I would think FF Invisible Woman would be all but guaranteed.
Oh, also, I agree with you 100% that Dagger and Gamora would make fantastic additions to the game. I'd love to see both Cloak and Dagger but if they were both released I would hope there'd be some very cool combos between the two of them or something. As for Gamora, I think she has the advantage over Dagger because of her GotG connection. A character I'd LOVE to see is Adam Warlock!