According to the Hollywood Reporter, Universal Pictures has picked up the project Wilson is co-writing with fellow actor Matt Ross and will be produced by Jay Roach (Borat, Meet the Fockers, etc):
The story follows two down-and-out community theater actors who think they've accidentally killed a co-star. In a panic, they go on the lam and hide out in a Renaissance fair.
"It's a bit like 'We're No Angels,' only funny, and in a Renaissance fair," Wilson said.
Apparently Rainn is a bit of a faire geek, growing up playing Dungeons and Dragons and attending ren faires when he was a teen. So basically this is his opportunity to talk in broken Elizabethan English and flirt with wenches behind a character, just like the rest of faire attendees do.