Sorry to be a buzzkill, but I doubt this a little. I can see the Steam Box announcement, definitely see that, but I don't think that the third announcement will be Source 2, due to the fact that the announcements are pertaining to Steam itself, not any game or game engine. Also, I believe that...
So... here's what I'm thinking. Let's assume that the circles (within the circles) represent Steam itself. So, the first circle is just one circle. That might mean the first update would be an update for Steam itself in its entirety, most likely Big Picture mode. The second circle contains one...