Seeing news reports last night on 2+ hour long lines at various airports leads me to believe that air travelers are/will soon reconsider flying in the near future. That may result in some travelers that have the time to take Amtrak. But then the 'close in dates' higher pricing (aka, 'yield management' that was started by airlines shortly after deregulation) will likely deter all but the most urgent-need travelers from taking Amtrak.
On the other hand, if these delayed/inconvenienced air travelers contacted that representatives in Congress about how the shutdown is hurting them, THEN, perhaps, BOTH sides will be willing to negotiate in the White House.