Well the books point other wise at least until further evidence. And i don't see any hope in him coming back after Walon Vau searched and found nothing on Kashyyyk. And now the Republic Commando's were shifted to Imperial Commando's so the best to hope for is that he got rescued from the Separatists that captured him by the clone Rebels or such. xD *cough* or he became a bounty hunter *cough*.
Karen Traviss wrote these books and said it officially: Sev is nor dead or alive, she just can't say anything about him, because it's forbidden. That's why she couldn't say that Vau found something. It doesn't mean Sev is dead. He's not.
Because LucasArts want to keep the mystery to maybe make a sequel to the game, but it's business so they're still not sure if they will make one or not. But they keep Sev just in case.
Yeah i know what you mean. The team that worked on SW:RC owns the rights to Sev and the Republic commando's. But still if you use common sense of who captured him(Separatists/Trandoshans) its doubted that he's alive. But best i can say is M.I.A. but if he's not dead im really curious on how he made it out alive. Then again its Sev.