From WaPo:
Texas Republican Sen. Kay Bailey Hutchison announced today she will not seek a fourth term, the first incumbent up for reelection in 2012 to retire.
"I am announcing today that I will not be a candidate for re-election in 2012," Hutchison said in a statement released this afternoon. "That should give the people of Texas ample time to consider who my successor will be."
Current Lieutenant Governor David Dewhurst, along with Ron Paul and a few others are rumored to be considering a run at the position. This will shuffle the deck for all the positions they will then vacate.