I don't really know what to expect? Valve's always seemed to be a pretty secretive company, so besides sequels for existing games, there's probably nothing else that is actually possible to guess. I would like to say revamp the original Half Life for seventh generation consoles, but I'd assume I'm in the minority of people who want to play Valve games on a PS3, and it's availible on steam, so I really can't complain. And it's kinda funny how anti-console the Steam forums seem to be, so whatever. Even though Valve's primary focus is the PC, my guess would be that the next big thing they make (HL3) will be for the PS4/XB1 if the games are running on a new engine.
You ask to discuss Valve games, and go on about consoles for a paragraph. Wait, that's what you wanted, right? Right?
Ninja'd: Oh, if we're talking about game specifics that could be fixed, then I'm not the person to ask, only having played HL2 and Portal.