I've wondered this very same thing. There are some excellent posts in the NW forum that attempt to analyze whether NW will follow suit or not. If they do, you have to wonder about the others, especially US Air, which tried a similar, even more restrictive move a year or so ago.
I would love it if Randy would weigh in on this question, as I think it has profound impact on the frequent flyer world as most of us know it. Randy, any plans for some "state of the union" thoughts in light of what has transpired this week?