I love Perkins, but this is a tough call.
Right now he's exactly what we need, but as others have said, in a couple years we're not going to have the fantastic offensive players we currently have now. Unless we can replace Ray, Pierce, and KG with players who can take up the slack on offense, we're going to need a center who is more offensively oriented.
Perk is a perfect center to go alongside a PF who is an offensive force or who can play away from the basket, but if he's not surrounded by stars he's going to look like a liability.
I think Rondo is going to have a similar problem in a couple years, though, unless he improves his shooting.