Lol, I started a thread like this aswell. I think they should. As for everyone who says there would be too many problems, THAT'S WHAT BETA TESTING IS FOR. Plus, there wouldn't be many problems that haven't been seen in games like World of Warcraft, so there's ways to fix them.
Well, if there was a pokemon MMORPG, we would need to play as the pokemon itself, since MMORPG's consist of leveling up by experience.
Either that, or the charcter itself would get levels to capture diffrent type of pokemon.
I'm sure that if they tried, they could make something like this, but it would take years to make and would have to be updated with new pokemon or have to make a whole new version every 5 years. I can't even see them attempting anything like this for years.
There are actually many pokemon mmorpgs out there, mostly beta though, so... But the idea should work though, I don't see why nintendo doesn't put more concentration into one, considering how pouplar they've become. Just imigine what they could have done with D/P...