Actually, I had already looked in that thread, and VX had already applied for SNA (which I consider a committment) before WN made that announcement.
Yup. If you read the thread, you see the mentions of VX's planned service.
Also, it's a bit different to have WN come in at roughly the same time on your new route, as opposed to starting service on a well-established WN route (PDX-Bay Area). WN could easily decide "time for $29 fares for 6 months" without hurting itself too much (since they have a lot of network outside of that), AS would match, and VX's yields on that route would be trashed.
based on the prices I am paying for so-called cheap fares on AS, decent yields
To give you an idea, SEA-SFO is $49 o/w on AS for a lot of dates in January 2010. PDX-SFO's lowest fare is $114 (which, btb, is considerably higher than
SEA-LAX at $69, which is nearly twice as long). That's VX's influence on yields right there- totally trashing them (and you see why AS doesn't like VX very much). Now imagine what happens if WN decides they'll run some $29 PDX-Bay Area specials once VX shows up (WN is considerably stronger in PDX than in SEA, and AS is somewhat weaker- I actually think WN will decide to try and step on BOTH VX and AS's throats in this market by being aggressive in a fare war, since AS is downgauging a lot of PDX-Bay Area to RJs and Q400s).
VX coming to PDX is going to be great if you want cheap fares on the West Coast as a consumer, but the losses on yields can't suck VX dry- AS and WN have lots of cash on hand and they are hardly going to retreat meekly like UA did on SEA-LAX (they downgauged to UX RJs) on routes where they command a lot of market share. VX was meant to compete against legacies (UA, AA). Competing against two of the best-run US carriers (both of whom operate on the West Coast as LCCs) is a whole 'nother ballgame, and I think they will be VERY cautious coming into PDX.