No confirmation from Sounders yet. (Nothing on Chelsea, either.)
If the report is correct, it indicates a change of philosophy for the Sounders, who in the past have been reluctant to open the full stadium because of Portland and Vancouver's inability to reciprocate. This season, Vancouver's potential capacity has roughly doubled due to the move to BC Place -- if they also opened their full stadium for Sounders and Timbers visits. But Portland still seems to have the ability only to accommodate a limited number of away supporters.
Naturally, I'll click back in if confirmation -- or denial -- comes.
Here's the Sounders and MLS 2012 schedule.