The dates were posted to the TechEd website, http://www.microsoft.com/events/teched2008/default.mspx, saying that TechEd 2009 would again be one week instead of two as was done last year in Orlando (and as is still done in Europe for TechEd EMEA). This year it will be earlier too, May 11-15, and be located in Los Angeles. I can't remember ever having a TechEd conference in LA before, nor can I remember it ever occurring earlier than June.
This also means that there is only one week in between TechEd 2009 in Los Angeles and MMS 2009 in Las Vegas. My suggestion: make it a three-week trip and take a week of vacation between the two :-) It's a nice four-hour drive between the two (well, depending on how long it takes to escape the LA traffic), through the mountains and the desert.