We're not sure at this moment if they will return. There was actually a rumor that Billy was going to be in RE5 because his voice actor posted something about Billy being in RE5. Though he quickly removed that so you can't see it anymore on his website. http://i16.tinypic.com/53q2h6d.jpg There are rumors as well that where Chris went in RE5 (in Africa) has some connection with Billy as well because remember he went to Africa and was ordered to murder a village filled with innocent people. (Of course Billy didn't do anything, but he was blamed for the murder.) All we know for Rebecca is that she is alive. In RE2, you see a report by her that states that Billy "died." The last game she was in was Umbrella Chronicles, only because she was in RE0 and RE1. (At least it's confirmed that she survived the mansion.) There is a hint from Resident Evil Degeneration that they might a possible new CGI RE movie and this time Rebecca will be in it. (Hoping she'll be in the games more as well.) Little is known about Carlos. All we know is that he escaped Raccoon with Jill. But who knows what he has done since Jill and Chris are still partners and they say nothing about Carlos. I am hoping they'll bring him back. They did bring him back with Jill in Umbrella Chronicles. (Where they remade how he looked like.) So there is the possibility of bringing him back. Hopefully all three characters show up again and also Barry. Hope this helped.