1. There will be 12 companions if Larian is now allowing for non-origin companions. One for each class. Also starting to think not all companions will be in Act 1 - but that we will meet some of the non-origin companions later into the game.
2. I think now that we know the release date there is a good chance of rather than doing a patch now and one in March/April they may just give us this patch and then go radio silent on new content until release, while amping up the marketing. But this is coming from someone who isn't a dev - not sure the amount of work it takes to maintain their Early Access branch vs. the release branch.
3. I would not be shocked if at release Larian drops a surprise race and/or class into the game.
4. I bet what we saw of Baldur's Gate was just a glimpse. Someone from Larian commented something along the lines of "You ain't seen nothin' yet" in response to someone talking about how cool the shot of Baldur's Gate was. Wouldn't shock me if the city is a massive place to explore, especially given the amount of time this project is taking.