My two most optimistic hopes were that some companions would be introduced later (for flavor! whether tadpole'd or not), and that we would be able to recruit all the companions and switch them out easily at camp, since I typically like to try out all the companions and combinations. For the latter, honestly I think it's enough to have that option for the first act. If you don't like where the story goes with the companions you commit to for the rest of the game... Maybe that's what a replay could be for, seeing what happens with the rest of them in later Acts?
If a companion I chose has a big conflict with my character later on, I'd consider that kind of interesting and not game-breaking. But I don't expect the kind of conflict that would result in a scripted character death or choose-this-person-over-that-one-or-else-I'm-gone situation outside of Act 1. That's not to say I don't think characters will develop or have conflicts, but maybe those specific dramatic conflicts would be established earlier on to avoid an empty spot in the party scenario (because if companions aren't alive or introduced in later acts, we can't really expect a BG2 Spellhold switch 'em out solution).
As for my first extremely optimistic wish... It was a long-shot anyway, and this storyline does lend itself to something preventing every single companion option from moving forward.
And we do know there will be more companions coming at full release. We can't say for certain that the current limited companions are the only ones we'll see for those respective classes.
