That's been a source of concern for me, actually. I definitely have some degree of proprietary pride at my City of Heroes and City of Villains characters, and the possibility of that world ceasing to be before I can achieve the arc I want to achieve is troubling at best.

Of course, there are games out there like EVE Online that are pretty much GM-free and entirely based on player interaction. In those cases, you'd just need stable server space and a cadre of fanatics.