Or he can pull a Kevin Willis and play until he's way past it.
I know it sounds unrealistic, but I can see CP3 staying here for longer.
24-25: Starter.
25-26: Castle's backup.
26-27: Third stringer and player/coach, hoping Wemby carries him to a ring.
Looking around, obviously things change during the season, but not many actual contenders will need a backup point guard, even if his name is Chris Paul.
If we assume that 8 teams are legit contenders (Denver, OKC, Minny, Mavs, Celtics, Sixers, Bucks, NYK), I'd say that only Denver needs a legit backup point guard, others have different needs when it comes to ring chasing veterans.