What I think will happen is...
The Celtics IMO(Ive changed my opinion) needed this trade. They were going to lose Rogers to FA. They needed a big man, who can rebound and is a legit post player(although Baker is still not near his once All Star status). By doing this trade, they were able to get that. There are 3 different lineups I can see them using.
SF Brown(assuming he improves)or EWilliams
Personally, I think Baker will start. The C's wont be paying him 10+ mil to come off the bench. Dependng on the team they are playing(if its an Eastern team), I think Baker will be playing C.
The Celtics aren't screwed(except capwise in the future). With Baker, they have a legit post presence....one who bullies in, not an outside shooter. Assuming JR Bremer, Sundov, Cook, S. Williams, and Kedrick Brown continue to improve, thats a pretty good bench(also Battie, if he comes off the bench.)
Walker and Pierce will keep the C's out of the lottery and ultimetly decide how far the C's go into the playoffs. But players like a Vin Baker, could make a huge difference when they need that extra rebound, or someone to help take the scoring load of of Paul Pierce and Antoine Walker. The problem is, they will be relying on unproven PG's in Delk and Williams and young, very inexperienced PGs in Cook and Bremer.