While many
Pokémon fans would like to see an MMO of the franchise, there's a good reason that's never likely to happen. The game series' director, Game Freak's Junichi Masuda, wants people to meet in the real world, not through a screen from the comfort of their bedroom.
Asked in an interview whether the series will ever go fully online (or whether the next big game might be for the Wii), Masuda said, "At this point, we're not thinking of going in that direction. Trading is a core concept of
Pokémon. So when you're trading, you meet with a friend and decide which one you want and which one they want. I would like to emphasize real-world communication. You don't see each other online."
It should be noted, however, that while that's a lovely idea, the likes of
Pokémon Platinum and
Diamond and
Pearl have online multi-player modes, not just features that make use of a local wireless connection.
It's also worth noting that a 'fully online' version of
Pokémon, be it an MMO or a multi-player only title, wouldn't exactly be playing to Nintendo platforms' strengths.
Source: What They Play