What if the two of the Villains in the Season are Todd and Travis, out for Revenge against Arbiter and Chief for leaving them behind after the Move? I know that Cortana is alive (until she was killed by Chief) and that nearly all of Season 3 has been retconned out as themm being left behind. Too unlikely?

Adam definitely does have potential, and as much as I wish to jam my thumbs through his neck I do want to see him return.

Kylie, however... Kylie would make a superb villain. I mean think about it - Kylie had so much motivation to destroy the poorly-named "Online Multiplayer Network" (simply calling it Xbox LIVE too complicated?): to get revenge on her perceived view of males (can't remember her exact insult) and to get enough money to escape her father, but now that she's been hung out to dry by Clyde, who left her to rot due to her own "incompetence" dealing with Arby and Chief; I can see her going out for vengeance against the toys, or their avatars, or whatever.

Duncan; no. He didn't get "picked off"; he left solely because he wanted to remove the TOSERS. He quit CT because he didn't want the network axed, and so he has no reason to pick scraps with Arby or Chief.

Trent; Trent's been done to death. He's failed twice and quite honestly if he takes a third shot he's a bigger retard than Master Chief.

NO. MORE. "FRAGBAN."

So all in all the only two characters I can positively see returning (or at least should return) are Kylie (a character who has a hatred of the protagonists, the XBL community, her former clanmates, and pretty much the entirety of the opposite sex) and Adam (a bastardly little bastard that fans hate to love and love to hate.)