Well, I think this just about confirms that the files that we found, and the code inside them, were part of a secret build of Valve's next-generation engine.
A few days after we found the files, Valve has removed the entire /vproj/ directory from everybody's hard drive. But the new Hammer icons are still there, and so is valve.py - the file that briefly mentions Ep3 and Alyx.
Here's a recap of what the code in the files told us about Source 2 so far...
These are exciting times for a Valve fan!
- Source 2 is in the making, and it's next-gen.
- Hammer is getting a big update (will include a scale tool, paint tool, several new terrain editing tools, and more).
- Source 2 may have full support for 64-bit systems.
- The content pipeline is getting an overhaul (new file format for world models, new standard file paths)