I'm not sure if Hellboy 2: The Golden Army has actually been dropped by Sony, as is being reported, rather than just not picked up. Whichever the reason the Guillermo del Toro sequel to the Hellboy movie has a little update and in it he says that Sony has bowed out and other studios are looking at the film.

From Superhero Hype:

Futuristic thriller "Killing on Carnival Row" is set up at New Line, with Arnold and Anne Kopleson producing through Kopelson Entertainment. A screenplay has been delivered, said Del Toro, but with no budget nor cast, project has still to be greenlit. Other majors are reviewing "Hellboy II," which was at Revolution Studios, as Sony has bowed out.

Technically I guess you could say that they have dropped it since they did have it before, but then I would expect they always had an option to decide once they saw the script. It would be interesting to know if they decided to say no after they saw the script, or if this was a decision made beforehand.

I don't think it's so much of a worry, del Toro is proving himself a worth writer\director and there's a lot of demand out there for another Hellboy story (isn't there?) so why wouldn't another studio say yes? Superhero fatigue perhaps?