Valve has officially confirmed to us that they will be attending E3 2012.
Earlier this year Gabe Newell did respond to some fan mail about E3, and he said that they "are not announcing anything at E3... We are going to be showing stuff everyone already knows about (CS:Go, Dota 2, 10' UI, ...)."
But in today's email, Doug Lombardi said that Valve will have some Counter-Strike: Global Offensive stuff at Sony and Microsoft's bustling booths. And a small group from the Steam team will be at E3 on business terms only, so they won't be holding any dedicated appointments with the press.
There was no mention of the "Meet the Pyro" short or the 10-foot Steam user interface, but those are believed to be released later this year. Perhaps we'll see that stuff at PAX Prime?
Speaking of PAX, if you're a Left 4 Dead fan and if you're attending, Valve wants to know about it. Perhaps they'll be bringing some L4D action to PAX as well. You can let them know via their Facebook orTwitter.