Left 4 Dead has to make a comeback. So does Portal. But for now they seem stuck on Dota 2 and trying to go where the money is. I mean, Artifact: the Dota Card Game? Really? Is this really Valve?
They could create a new IP every once in a while as well, instead of going after the trends.
I'm pretty sure L4D and HL will return some day, and the day that announcement drops will be treasured by many. But why it is taking so long, I can't imagine.