According to an article in PlayStation: The Official Magazine, InFamous 2 is a possible title to come out this year. The most interesting part of this rumour is that InFamous 2 hasn't been officially announced yet.
A Sony representative has commented with the usual "we do not comment on rumor or speculation," but it is interesting that a magazine officially endorsed by Sony has written an article on a game being published by the same company.
It's not really like a sequel to a game like InFamous is overly surprising, as it did pull off 1.35 million in sales since May of 2009. That's most likely enough to warrant a sequel.