You read the title right; Valve has reported that they are not going to be releasing/announcing/teasing/previewing/etc at E3 2011. 

"Lots of folks have mailed asking about appointment times, etc., with Valve," said Valve's go-to man Doug Lombardi. "Well, we are not showing any titles at this year's show. So no appointment is needed," he added. 

A lot of gamers are ever-waiting for Half-Life Episode 3 to be announced but Valve is just bouncing back from their release of Portal 2 and details of HL3 are nil.