I was just thinking that Pokemon would be an excellent MMO. I've heard it argued that Nintendo would never go down this path because they wouldn't want to alienate the fans that made the series such a cash cow.
I always thought they could keep on releasing handheld titles to appeal to those not interested in an MMO, and release expansion packs to keep those interested in the MMO up to speed with the latest Pokemon, Gyms and other such things. Nintendo wouldn't be alienating their audience if they proceeded this way; they'd be gaining a whole new one, thus doubling their revenue.
Someone really needs to make this happen.