Portable gaming has never been more popular than now, and it might eventually be the dominate form of gaming in the future, I actually think it will too.
It could only be for the best, too. Imagine still getting a Shenmue III that has the same level graphics as the first two a few years from now, but on a handheld. That would be amazing especially if you could optionally host the game through a television.
My biggest issue with handheld gaming and eventually the overall future of the medium is that game boxes will no longer exist. I hate to think my children or children's children might not be able to have the same satisfaction as I did when I got a new game to check out everything that was inside the box and look at all of the art on the inside, the story in the manual, etc etc.