Valve might not be making it to E3 this year, but it sure has a lot to talk about lately. The most recent topic is Dota 2, and the fact that that it looks to be the first game to be built on Valve's ever-forthcoming Source 2 engine. A full reveal is due this week, but what we know now is that the game will be updated to a "new engine", and it doesn't take much brain-power to realize that it's Source 2 involved.
It's important to note that Dota 2 Reborn isn't a sequel; this major update will just be one of the many that have helped evolve the game. This revamp is a lot more than just improved graphics, though. The entire UI is going to be overhauled, and Valve is striving to cater better to the noobie with far better training tools, which includes guided bot games.
Other improvements include being able to hook up with your friends easier, the ability to spectate a variety of matches with stats tracking, and much more.
On the technical side, it's hard to say all of what this upgrade to the Source 2 engine will bring. As it is today, Dota 2 runs well on a wide-variety of hardware, so it won't be surprising of Valve doesn't go "all out". You'll remember that when Portal 2 was released, its graphics were far from top-rate, but that didn't dampen the quality of the game much at all. Valve's ultimate goal is to make its games accessible to as many people as possible.
We're sure the full reveal is due imminently, and this is definitely one to wait for. With Dota 2 constantly peaking Steam's most-played charts, it's no surprise that Valve would want to make it its first Source 2-based game.