I thought this was posted already... anyway, I do think there is room for him in the rotation. The deeper the better, and he brings some defensive skills with his length that VladRad and Luke just don't have. The Lakers do need him back for the playoffs, IMO.
The Lakers are doing just fine right now. With the team not at 100% and they have been winning the way they have, that is what any sports fan wants, as long as everybody is good (Kobe definately won't be 100% but...) then it doesn't matter. If Ariza is comfortable in whatever spot he is in come playoff time that makes the Lakers even more dangerous.