Mag lev, huh? Hey that sounds cool, they can build it right after they finish the light rail in 2006, or was that 07, no it must have been 08, 09, 2010????
Seriously, while a mega-regional airport might make some sense, I seriously doubt Portland, Seattle or Tacoma (note they are in alphabetical order, I'm not picking on or showing any preference here!) would be willing to swallow their collective civic pride and give up 'their' airports. It took congress to make Dallas and Ft. Worth play nice, and they are only 30 miles apart, not 120!
Realistically, I see the 3rd runway (eventually) getting finished, some moderate additional ground facilities being built, and a 15-25 year debate about what we do next. In other words, same old, same old......