They will not move it. With signed contracts that I'm almost sure would force them to pay for the space even if it's not used, moving it is not financially feasible. In addition once it’s been announced some players start booking right away. If they were to move Nationals they would face likely lawsuits from people trying to recoup some or all of their losses.
That being said, I wonder why research wasn't done to prevent this sort of thing from happening. (Maybe it was thought it wouldn't have an impact?) It will keep players away, because not only can you not book a decently-priced hotel anywhere near the Convention Center, but if you rent a car… where are you going to park? Public transit is an option but not one everyone is comfortable with, plus it’s not always 100% reliable and with the other conventions booked it may also be quite full. Perhaps a cab between the hotel and Convention Center would be ideal, but that costs money too.