If true, Gervais will join Ty Burrell (Modern Family) who was confirmed recently to feature as a "lazy Interpol agent". While it's unconfirmed that Gervais will also come on as an agent, it is likely that he'll fill in the lead role that was taken by Jason Segel took in the 2011 movie. Gervais did actually film a cameo scene for The Muppets which was cut due to time constraints.
While Segel isn't returning, director James Bobin (Flight of the Conchords) and Nicholas Stoller (Get Him to the Greek) will return for the untitled sequel. In a recent interview with ComingSoon, Stoller said that, "we kind of felt like we completed Gary's story in the first one and he's mostly interested in writing stuff for him to be in, which makes sense, right? He didn't want to go on and write the next one. I was like, 'Do you care if I do it with James?' He's like, 'Of course not.'"
As of yet, none of the other human actors from the first movie have been confirmed but we can assume that Muppet performers Steve Whitmire, Dave Goelz, Eric Jacobson and Bill Barretta will return. The movie is apparently set to be filmed in Europe and no release date as been announced.