Have they said they will lock the party? I got no real indication or feeling that it was the case when I finished the EA. But it does seem like you can't have all the characters with you if you make certain choices.
Pretty sure Wyll will not take kindly to you joining the Goblins, and Astarion get's very crabby if you get angry at him for being a vampire.
All in all it doesn't seem to me that the way the game is set up is going to force a locked party, in fact it seems like the opposite. If they force the party, they cannot have party members leave the party, or else you are stuck with just 3 members.
Yeah, I was actually pretty sure they wouldnt lock It, since you got so many camp followers already, why not have the companions you are not using when leaving act one follow too, don't know if I missed some conversation on game or Interview, but I got no indication this would happen at all
Same here, in game I have not experienced anything that indicates that the party is locked, was something said about it interviews or something? It would be a pity, and needs to be made very clear if/when/how it happens to not accidently lock people into a party that they don't consider their main party.
It was mentioned in Community Update 7 in the q&a portion. Quote below. I am perfectly okay with companions leaving in result of choices. I think that is fine, and pretty cool.
"Will companions be interchangeable during long rest?
Yes, at the start of your adventure your recruited companions will be at camp when not in the adventuring party, and can be swapped in and out at camp. Just like friends in real life!
After the first act however you are going to have to commit, also just like in real life."
Edit: To me, the quote seems to imply that after act 1, companions become no longer interchangeable. Which would be a shame. I like companions leaving if they don't like you, but not having your party locked.