A Pokemon MMO would probably be in the same vein as Destiny but mixed in with the current Pokemon Bank, a new version every few years in order to bring in a new region and reset everyone to zero, but with Pokemon Bank functionality activated a year or so after launch, so people are forced to use the current gen Pokedex for early Tournaments and such.
There are other logistics which could prevent a possible Pokemon MMO from happening compared to continuing the current way of things, but I won't say any of that to prevent this thread from derailing too much.