If the Clips and Billups can sell KG on signing on, I don't see why he can't play at least this year and next, and possible finish out his contract.
If I'm the Clippers, I'm going all in this year. If they make the move for Garnett and make a strong push in the playoffs, CP3 is not going anywhere. That team is now going to be a magnet for vetmin ring chasers and good players discounting their services by settling for the LLE or MLE to play in LA for a contender.
By trading for KG, you wipe a whole lot of past stench off your franchise. Healthy, that team is going to be an extremely difficult playoff out in the West, and has the two pieces of Heat kryptonite - a mobile center who can play inside and out, and the best PG in the game. Considering that they're not going to be able to pay Bledsoe in two summers, and that DJ, although solid, doesn't have a ton of offensive upside, they'd have to think long and hard about making that deal if KG is on board.