If a developer looks at a game and essentially says "I don't know if we could do this and be sure not to fuck it up"...I got nothing but respect for them not doing it. We complain all the time about people cashing in rather than making a good game, it would seem weird to complain about Valve doing the opposite. I also wouldn't expect them to sell off or loan the IP out to someone else. If Valve is worried about disappointing people if they do it themselves it doesn't make sense to hand off the controls to someone else to possibly fuck up.
It isn't like the world is short on games to play.