Project Borealis is a fan-made Half-Life 2: Episode 3 based on the Epistle 3 script posted by former Valve writer Marc Laidlaw. It's been in development since 2017, and today the team showcased the first footage of some new maps, along with a shootout with some creepy homunculi still awaiting their textures.
The update explores the level design process, showing off a chilly cave's development from a section of a script to an in-game map that's had its first art pass. We also get to see some of the progress the team's made with the episode's physics, and it's going to be switching to the new Unreal Chaos Physics system and AMD's FEM deformation tool when they're released, but they've already been doing a lot of experimenting with PhysX.
So we may see something in 2 years or so?
I went back and finished HL2, Episode 1 and 2. What a blast, and looking back now on better hardware, that HL2 game really set some new standards for gaming. Playing on modern hardware the game is silky smooth.