From the musings going on in Congress and at the White House, it seems that it's more a question of when, not if DCA will re-open. Here's a suggestion that I am employing on all my reservations... tell the res agent to put in your profile some sort of waiver, eg. "the only reason Mr. X is flying from (IAD/BWI) is because DCA is closed, please waive re-ticketing fee to DCA when it re-opens"... it might work, it might not, but at least there is some precedent in the PNR for you to fall back on.