DCA is my home airport and, because I live in the District, far more convenient for me than BWI or IAD, but the VA and MD Senators made a compelling case to me as to why this shouldn't proceed. The airport is already 10 million or so passengers per year beyond what it was built for, and the FAA estimates that adding an additional five round trip flights would increase delays by 725 minutes per day, for a total of 12,734 minutes of overall daily delay at DCA. This year, we're already at about 22% of all flights being delayed. Ad in a near crash on the intersecting runways last month, and I'm unconvinced this is a good idea.
Part of the problem is that DCA is both owned by the federal government (so Congress gets to determine the slots), and it is uniquely convenient to Capitol Hill. A lot of the existing exceptions to the 1,250 mile perimiter rule are owed to Members of Congress who want easy nonstops back to their states/districts. For example, Alaska Airlines has a daily morning and evening nonstop between DCA and SEA largely because the Washington State Congressional delegation saw to it. If you get on AA's evening flight from DCA to LAX on a fly-out day, you'll encounter numerous Congress members from Southern California, etc. etc. So it's possible this is a foregone conclusion and the slots are coming.