Film Buff Online has a source (one that actually has a name, hurrah!) that says he talked to Billy Dee at the Monster Mania convention this past weekend:
Billy Dee said, he has been asked, but hasn’t decided if he is going to do it or not yet.
If true I think It could be a fun cameo but nothing more. I love Billy Dee. But he’s somewhat become a parody of himself at this point. He’s amazing on Robot Chicken, Detours, or the Jimmy Kimmel show but I’m not sure it would work if he reprized his role of Lando as a main Character.