It will probably continue to lose popularity, but as long as it still has a fanbase and games are still being made it's really not "dead". I agree that it has a very good chance of becoming a classic like Mario, Sonic, Zelda, Final Fantasy, etc. However, I think we should actually HOPE that they find a good time to stop making games. After we get about 700,000 Pokemon the games will grow old and it will be impossible to remember all the species. If they keep making games without adding the Pokemon, though, we'll more than likely begin to get bored with just the ones we have now. I love the concept of the Pokemon world, but I personally think that there are ways that they could have set up the games to prevent this repetition. At this rate, the games will eventually become exactly like the anime is now. However, I plan to stick to Pokemon at least until it completely falls apart ^^. And I'm actually happy that it's not insanely popular anymore; extremely popular things tend to get on my nerves.
This is kind of offtopic, but it certainly seems like Pokemon will outlive Digimon (if it hasn't already). It's still too early to say if it'll outlive YGO or not though.