It doesnt matter.
If they did make it and it was fantastic and your fan of the franchise, your tellling me you wouldnt play just because of the other games.
That's ridiculous.
Out of all the games from the series (which are made when the movies come out just for the money), an MMO is probalby the only perfect genre that Harry Potter would do well.
Just think of being an Auror going after Voldemorts minions in real time, and those minions are real humans. It would be awesome.