Since as far as i remember, Swen told us that there will be some more in the future, when we at first started talking about all our companions being evil, or at least not exactly good ...
That's a good point. I have been assuming that current selection covers evil-neutral choices, and good origins will be Minsc/Helia. As it is, opening act1 might be rather short on good characters without some extra faces, though the question is how Larian treats "good" - some might interpret Gale or Wyll as good.
With there being two "good" companions, maybe the "evil" side will also get two?
I was thinking about it as well. If Minsc and Jaheira can turn on us, it would somewhat make sense to have someone else cover evil path. I am also thinking of our act1 origins and how they could be split at the end of act1 depending on our choices. That we we get our starting companions leave us and turn into antagonists, while we get a boost of new companions later in the game.
I would be up for seeing even more old faces from BG1&2. There have been mentiones of Edwin being the receiver of the iron flask from act1 - what if he, and someone else was the evil companions, and continuing feud between Minsc and Edwin would be a nice callback to classic games, though I have no clue how Edwin could still be alive (though, if Minsc can, so can he I suppose).
On a side note, I must say the recent trailer made a positive impression on me. Mixing old and new gave me "the next generation" kind of a feel. Act1 might focus on new faces and places, while act2 and Baldur's Gate might deepen the connection to previous two titles.
