As much as I would love that, Nintendo can take the Pokemon formula, think of two new colors/metals, add 100-150 new Pokemon, add a gimmick or two (animated sprites, triple battles, fashion shows, breeding, etc) and it will shatter records.

An MMO takes a lot of money to develop, economically it doesn't seem smart when just another Pokemon game will do great. When a new Pokemon game DOESN'T break records, globally, is when we'll see games like an MMO (Also why I'm assuming there aren't any experimental Pokemon concepts like Hey You Pikachu and Pokemon Snap when Pokemon was still new) but that might be a little while.