Isn't that precisely what we got at release?
Also, the role of companions in this game is significantly larger than in KotOR. That being said, some of the more drastic elements of SW:TOR's story in beta (such as killing companions) were dropped due to feedback.
Not really. I haven't played all of the stories but I haven't seen a point yet where what you do significantly changes the game story. You might have bits where it's 'Oh no, that's not nice/good!' But then that is soon forgotten. Presumably because it would've been too hard to track multiple plot lines with 8 stories.
I didn't know that about the companions in beta. Interesting. Shame that BW pulled that.