What's a little confusing to me about the OP is that many of the flights to DCA/BOS/IAD are operated by CoEx.

So, if what the OP relates is accurate, should we expect mainline flights to/from DCA to operate out of T-C while the CoEx flights to/from DCA will be in T-A?

That seems like it would create a lot of unnecesary confusion.

BOS currently has 3 mainline and 1 CoEx flight/day.

DCA has 2 mainline and 3 CoEx flights/day.

IAD has 5 CoEx flights/day (no mainline).