This is sounding relatively definitive: Pierce County Executive John Ladenburg seems to be positioning himself for a run for attorney general.
The Tacoma News Tribune's political blog is reporting that Ladenburg has been meeting with state Democrats, and will decide within a month if he will enter the race. A county spokesman said "he’s seriously considering running for attorney general."
Pierce County is an excellent launching pad for state office - it's a large and pivotal county. And there appear to be no other publicly interested Democrats for the job. Against that, Republican AG Rob McKenna is not likely to be an easy target; he seems increasingly dig in where he is, and his campaign has been underway for a couple of months or so.