I think the point when they no longer have a lock on the merchandise revenue via trademark will be when they give up the name.
And that's where they - and the NFL - get a lot of money from. Strip them on the trademark and anybody and his brother can sell Deadskin items and not have to pay a fee. So just drop the nickname altogether and tell the NFL to screw themselves if they don't like it.
I confess that once Washington has been beaten into submission my fear is that my own Kansas City Chiefs will be the next target. Then the Cleveland Indians. And the Chicago Blackhawks.