I think Move will have a much more gradual type of growth since it is targeting a much more diverse demographic than Kinect (which seems to be targeting primarily casual gamers). I can see more and more core PS3 gamers pick up the Move as the library grows.
As a core gamer who owns all three major home consoles, I've been closely following these motion control accessories to see if Move or Kinect would be worth a purchase. I like the idea of controller-less gameplay in theory, but in practice, it's slowly becoming apparent that many current genres are going to have a hard time being translated for Kinect. Many of the more "core" games that have been shown seem to be on-rails, which is definitely disappointing.
With the Move, since it uses controllers, you can see a lot of current genres incorporate the technology, so it can be much more easily applied to hardcore games. The fact that Move capabilities are being put into hardcore games like Killzone 3, LBP2, Heavy Rain, Resident Evil 5, and so on, is a tremendous incentive for current owners to at least give Move a try.
At least in the beginning, I can see Kinect being more successful at bringing in new, casual gamers into the install base, whereas Move is probably going to be more of a hit among its current install base.