To answer that, you'd have to ask "what, exactly, would AA do if the WA is repealed?"
If AMR follows through (as they probably will since they would admit "defeat" if they didn't expand greatly out of DAL) and picks apart their fortress to compete at a not-even-cross-town airport, they will potentially become vulnerable at DFW as well as create an expensive operational mess. THAT would take stock down, of course. AA is used to defending DAL against smaller players and they have long enjoyed non-confrontation with WN but with the repeal of the WA, that may all change. HOWEVER...as AA constantly states that DAL is really the same market at DFW and not a separate one, I have to agree with the analysts that it is really foolish to separate ops to compete within the same market. Just as WN doesn't split between DAL/DFW, MDW/ORD, FLL/MIA, it just wouldn't be a wise financial decision for AMR to split. If they carry through, investors will be less supportive than $20/share.
But then again...AMR is finally emerging from the depths of recession and TWA-aqcuisition and they are in a stronger financial position than most. If fuel spikes again next year, WN will be no better off than AMR. Will stock rise much more? I don't know. As an airline stock goes...I tend to think that if AMR stock rises much more, it is definitely a bubble and I don't know as though I'd be willing to purchase something that could burst at any time. And as always...airline investors are the craziest group of people I know. Willing to throw a buck at anything that says "airline" on it. They don't behave like a normal investor.