The HL3 memes don't even seem fair to use anymore. I don't even want to un-seriously make joke fun of them at this point. They are just genuinely doing so much for the community.
Given the org structure at Valve, it's going to take someone with massive hubris to say "I can be the one to lead the HL3 project."
That or Gabe getting off his megayacht to lead it (or tell someone their project is worthy of being called HL3).
(To be clear, I'm not saying it's a matter of ownership and personal brand. But someone needs to start the project and form a team around it. I don't think they're worried about personal brand, it's more an issue of reverence for the franchise.)