Kyle Horner took a look at the possibility of City of Heroes 2 in The Digital Continuum. He investigated some of what NCsoft has done before and gave several reasons why it would make sense for them to move in that direction eventually. There was a fair amount of skepticism, but it looks like Kyle may have called it.
Eurogamer reported today that NCsoft has trademarked the "City of Heroes 2" name. Now this is certainly not anything resembling a commitment to make the game, but it opens the door to the possibility. NCsoft could be planning to start working on the game soon, or they could just as easily be guarding against future shenanigans from those not affiliated with the game. NCsoft had this to say: "City of Heroes is a flourishing franchise and continues to be the world's most popular super-powered hero MMO. While we cannot comment on City of Heroes 2 at this time, NCsoft is proud of City of Heroes' success and is looking forward to future product launches associated with the franchise, including the City of Heroes Going Rogue expansion scheduled for release this July."
For now, we'll try not too speculate too much, and look forward to Going Rogue.