The series in itself will probably never die; it's just like Neon Genesis Evangelion. As long as money can be made from it, it will continue to exist. However, we probably won't see too many more generations after Gen V, so we'll just see spin-off games. There will probably be another pinball, maybe even poker or perhaps a pachinko spin-off. Sooner or later, we'll be able to look back and say, "Hey, remember when Pokemon was about traveling the world with creatures and striving to beat the best?" just like how older watchers of Evangelion are saying "Hey, remember when Evangelion was about ideologically sensitive material regarding the existence of God, the natural behaviors of the human mind, and the catharsis of a young boy who craves only love?" And now all you'll find is Evangelion pachinko and childish puzzle games.
In short, Pokemon will probably turn into another Evangelion, but will it die? Probably not.