While it's beyond the scope of this article to describe how you might implement a full animation system that uses subdivision surfaces, it's worth describing how subdivision surfaces and animation can coexist. If your game is one that stores the animated model as a series of full models, clearly you don't even have to think about it - subdividing those individual meshes will just work.
Skeletal animation is a somewhat more interesting problem.
This does have some downsides, though. Depending on the model and a host of other factors, the skeletal animation might cause the model to flex in strange ways or to exhibit increased rippling or unfairness. The other downside is that it doesn't allow your application to take advantage of forthcoming hardware that supports skinning on the card. Depending on the speed of that skinning, though, and on how many times you subdivide the model, the savings of you doing a reduced number of transforms may or may not be worth the loss of offloading. Since this is a scalable geometry solution, it's worth asking if we can adaptively subdivide based on curvature or distance to the camera.