Well, Heart Gold and Soul Silver just launched in Japan with numbers that would have matched or exceeded Diamond and Pearl if they hadn't been supply-constrained.... so I guess we'll see!

I'm a 20 year old college student and I know a ton of other people in college that would play a Pokemon MMO. My generation grew up at Pokemon's peak and the nostalgia factor alone would reel in a ton of players. With all the traveling and Pokemon they have now I'm sure expansions or microtransactions would be very profitable. Think about choosing which region you start in, pick your starter, then you can just go collect badges and catch a bunch of Pokemon. With all the PvP options the game would never really end considering they have like 400+ Pokemon now too.

Ok so you get in your pokemon MMO, collect 200 pokemons, play a couple hundreds duels.
Then what ?

You have to realize the huge majority of gamers ( those that make the bulk of a game like Wow) are not ready to spend 50 hours to collect 1 pokemon....

32 gyms, Elite Four, Battle Tower, possible bad guy instances, Legendary Pokemon (probably shouldn't be able to catch these), and all the traveling is a ton to do already. Adding in PvP, Pokemon catching, and miscellaneous tasks puts the play time total even higher. People in WoW will run the same instance over and over for gear and experience, which isn't very different from trying to get a specific Pokemon. I'm not saying it's perfect or a for sure success however I think it would be a lot of fun if done properly.

How have we lived without SugarTits?

Just imagine getting in a battle and having every 8-15 year old kid call you a f*ggot n*gger jew all day long.  No thanks.

I think people vastly overestimate the potential of a Pokemon MMO. I can't see it translating well off handhelds. What would the gameplay be like?

There's no way the game can be as widely re-playable as WoW is. MMO's (including World of Warcraft) are a social experience - the game remains interesting because of the interactions between players (PvP, or PvE instances). People pay monthly because there is always more to do. How can this be done in Pokemon? Group Pokemon battles?

The MMO genre just doesn't play to Pokemon's strengths. Pokemon sells tons because it's so damn simple - MMO's are the furthest thing from that. The fact that Pokemon sells 15mil+ doesn't mean much, Final Fantasy games sell 5mil at its worst, and FFXI could only grab 10% of that.

Let's put it this way - what will this MMO Pokemon game offer, that the normal handheld game doesn't? How much of the Pokemon audience will find it worth paying a monthly fee for? A normal handheld online Pokemon (not MMO) is enough - anything more immersive starts to overshoot customers.

I honestly don't think a Pokemon MMO (monthly subscription) could hold even a quarter of WoW's current userbase.