Pokemon will last as long as Mario.
Nope. See, Pokémon is a franchise that lasts upon that popularity of the two games released every three-five years or so, and then it grows an immediate structure. The anime that follows the same world of the game with the old characters that will never ever evolve, a few spinoff games, the community...
Now, I can't see the community giving up on their thing. Heck, I couldn't see this community disappear from the map if there were no Megaman games for ten years because you guys are just too damn stubborn.
But it is not a franchise that can evolve and bend as much as Mario. Pokémon are probably the one franchise that Nintendo just doesn't evolve at all (no, new features and 3D environments don't count, talking about the main game) and sooner or later, it'll reach a point where it either evolves, is whored out beyond belief, or people get tired of it to go to the next new thing. You know, kinda like what's happening to Final Fantasy right now. Still popular, but it's slowly descending.
While Mario? I don't doubt that there might be hiatuses in the future, probably when Miyamoto dies and the character goes into the Mickey Mouse territory of irrelevance-but-still-symbolic, but I certainly don't doubt that Nintendo will keep pumping out great Mario games for a looooong time, and through different kinds of interests and likings.