Latest rumor is this is just another way for Fox to establish dominance over the project. Supposedly Scott family and Rinsch are tight for obvious reasons, and by booting him, it infuriates the scotts and forces them off the project.
They know by the new media response and the fan response that the audience will be there. Thus they are free to bring in their own people to do a series of film their own way. I dont trust Fox decision making at all, and I doubt they have positive intentions.
See Alien 3.