ecureuil wrote:Technically, that wasn't Valve. It's just that the content was so well-made, that Valve offered a helping hand in placing it on XBLA, because PC users could just download it freely and play it. Valve have never added anything to Portal 1, aside from the altered ending.
They did add some extra stuff later as well (Portal: Still Alive on XBLA).
They are very passionate about Portal 2, though, so it's not unlikely to expect them to add something, yes. Co-op was structured into a massive hub for a reason. L4D2 DLC comes first, though. They said they'd work on that right after Portal 2.