OMG this needs to be a thing! But I don't think valve will have the funds or the patience to make all the little characters, the rules, the stage props, and advertise it. They're already making Half Life 3 and Left 4 Dead 3, so I don't think they'll have the time.
You kidding me? Even if they ARE making Half-Life 3 [which they themselves have not confirmed], I'm damn sure they'd promote this if they want to. I'm pretty darn sure that taking about 10 years and still counting to make a sequel for a game means that they are not exactly putting all effort into purely producing it. In other words: they damn sure would have at least a few people whom could go full-time promoting this.