They won’t do it with Source 2 (lack of “braking” according to the developers), they already have ideas (well anyway, no idea if that’s still the case), with SPOILER ALERT, Borealis in the Arctic, gameplay sketches (at the time Source 1) with Blobs that assimilate crab heads and adapt to the environment. Source 1 + Havoc already looked good at the techdemo in my opinion at the time, but since Valve doesn’t need to release games and only releases them when they know it’s going to be a slap in the face on all levels ( HL, HL2, HL Alyx to name a few , which changed everything when they came out), they’re waiting for the technology to be there, they’re lucky to have Steam which brings in a lot of money, so they’re taking their time. And again, not to mention the lovely Gaben who doesn’t want a “3” (HL3, HL2 Episode 3, etc.)… in short, we have to be very patient and hold on to hope…