In an interview with IESB.net Fox Chairman Tom Rothman was asked if rumours of a possible Deadpool spin-off were true.
Tom Rothman: Yes and no, I mean, Deadpool is an integral part of X-Men Origins: Wolverine, we are in the process now, of doing all the CG work to create that character at an A +++ level, that’s being done in truly as state of the art fashion as possible…
IESB: Scarring and all?
Tom Rothman: It will be very rewarding for the fans, let’s put it that way. It’s a high level endeavor because he figures importantly in the movie, so whether he’ll spin off into his own movie, if that’s what you’re asking, I don’t know the answer. We will have to see.
One of the main reasons Ryan Reynolds was cast in X-Men Origins: Wolverine was most likely to set up the character for possible spin-offs. Reynolds is a big enough actor to lead his own movies, so he must have took the small-to-medium sized role with the hint that more could be coming further down the line.