4chan has never been community that kept its secrets. A couple of examples include the new champion “Ekko” for League of Legends, months in advance. Along with the plot of Metal Gear Solid V.
So here’s what happened. Someone on 4chan posted a thread with a .rar file containing more than 2000 images and said that it was a puzzle related to Half Life 3. The images we named something like doguntextured(1). Users eventually figured out that the images were tiles and they were correctly numbered and not shuffled like they had previously thought. It took a sufficiently short amount of time and we were presented with the final image seen below.
The thread was posted on Reddit as well, and on both websites, the users started trying to decipher any hidden meanings. A little observation showed that there is a high chance of the model being from Source 2 (concluded after seeing the floor texture in the image, which is the one from Source 2’s world editor). Also, it could still be a really dedicated fan who made this but at the same time this could be real (because of the amount of detail in the model).
So at this point you’re probably better off believing that this never happened rather than getting excited and then disappointed. However, as the Viva is getting closer and closer, the world of Gordon Freeman returning is becoming more and more plausible.