The actor stuck around after the screening (and after the applause died down a bit) to talk about the film, and answer fan questions. Some of those were about the development, some were about specific scenes, and some were about the future of the franchise.
When he was asked what characters they wanted that they couldn't include, Reynolds echoed Director Tim Miller's reply, instantly saying "Taskmaster. We all [wanted him]." Unfortunately for them, it appears the movie rights to the character have gone back to Marvel Studios. When the filmmakers contacted 20th Century Fox about it, "the studio just called us back and said 'cha-ching.'" And that was it.
But then he started talking about "making more of these," which fans responded to with more boisterous applause. One fan yelled out "Sequel!" and another fan followed-up with "Cable and Deadpool!" and that wound up revealing something from Reynolds.
"Your lips to God's ears, my friend," he said directly to the Cable and Deadpool fan (I swear it wasn't me). "Believe me, that's being talked about." He gave a smile, a nod, and raised his eyebrows as if to emphasize the point.
Miller has also talked about Cable before, saying "If we don't put Cable in Deadpool 2 I think we'll be run out of town." It seems like that's now much closer to reality than those without behind-the-scenes access could know.