MAJOR SPOILER ALERT!
: Proceed with caution.
[spoiler]I almost always went to save Kaidan.. My squad almost always consists of tech people. So, it would usually be between Tali, Garrus, or Kaidan. I never really brought Ashley along for much anyways..[/spoiler]
Anyways, I highly doubt you will see most people from the first game. [spoiler]Ashley and Kaiden probably won't be there because you have to redshirt one of them. Wrex probably won't be there because you have the choice of killing him.[/spoiler] Garrus may or may not be there. The way you talk to him really ends up shaping what he's going to do after your mission's over, he tells you. Tali, well.. She's probably going to stay with the Quarian Flotilla. Liara, I suspect will be in this game. It's just a feeling.
Oh, and according to what BioWare revealed at E3.. [spoiler]the Normandy goes BOOM.[/spoiler]
EDIT: And on the note of more than 2 squad mates, I doubt it. They made combat much more complex. And from what I've seen, it's still a 3 member squad going out to fight. However, I know you can have massive battles now. ;]
They added a new heavy weapon category. The ammo is limited, but they are deadly. So, I'm guessing that has to mean something, no?