According to Bill Condon, in an interview with MTV's Josh Horowitz
, the Breaking Dawn soundtrack could possibly feature one cast member. The the deal isn't finalized yet so the Director didn't give any names. Mr Condon talks about giving nod's to the original Twilight movie & coming full circle stylistically & with having Carter Burwell & Bella's Lullaby on the BD soundtrack. Josh then asks Bill, "You have a very musical cast, are any of them going to appear on the soundtrack?" to which Bill answers, "Actually yes, I'm pretty sure."
So what cast member do you think it could be? It could be Robert Pattinson, who was on the Twilight Soundtrack, so that would really be coming full circle but it could also possibly be Jackson Rathbone who's expressed interest in having his band 100 Monkeys on the soundtrack. I hope it's Rob!