I wonder if, in general, Marvel is against the idea of funding and promoting a game where players could create their own unique characters; It seems to me that they're much more interested in monetizing their existing characters/IPs. On top of that, the MMO market just isn't what it was before. Frankly, an MMO where you start off as an Avengers or X-Men recruit, then could progress to a full member, eventually participating in quelling global threats would be amazing, but then they couldn't sell Captain America skin #531 for the thousandth time.