Deep in the code of Valve's Source Filmmaker software, references to what may be the company's next-generation game engine are made. The folks at Valvetime spotted multiple references to something called the "Source 2 engine," and other hints, such as icons (pictured above) were also uncovered. Try on this line of code for confirmation:
It seems that they've made no effort to cover up what they're working on over there. That's so Valve. So is this little bit from the company page:
Yep. Source 2. Source is amazing, but we all know it's getting a bit old. It's safe to say it won't be long before we see a bit what they're hinting at here.