I think with the proper coaching and a PG like Rondo to play with JaVale McGee could mature and become a 15 PPG, 10 RPG, 2-3 BPG center that would be a bargain in the $10-11 million per year range.
On the other hand, he makes Rondo look like Ray Allen at the FT line, and he might not mentally mature and just be a stats guy on a bad team type of player.
If expiring contracts and the C's first rounder this year and a future 2nd rounder would get him, I would do it and try to extend him. I think he's a better bet to become something going forward than anyone the C's will get in the high teens in the draft.