I tend to think it won't, for simple reasons: what makes DCA more prone to supporting high fares than any transcon outstation, like, say, EWR-SAN or SFO-MIA? And why isn't that market served by just having folks buy tickets on three-class planes on SFO-IAD?

And before you say: "it's DCA, limited supply"; I think the proper market's WAS, not DCA. Loads of supply there.

Also, if anything, there's an entire class of people who'll want to fly that route who cannot buy C fares: government employees flying on the public dime. And UA doesn't fly p.s. on transcon such as to give it away; that's the entire point of shrinking the p.s. cabin when they go from 3-class to 2-class lie flats (as well as going to C/E+/E-)- less supply, less upgrades.

As such, I think it likely the best revenue mix is filling up the plane with Y than giving away C on upgrades by running a large C cabin. It's rather telling that the only transcons AA, UA and DL run with enhanced premium cabins consistently is JFK. AA and DL could run their enhanced domestic F products on LAX-IAD/BOS/MIA. They simply don't. I suspect that's not because it never occurred to them that there's untapped demands for $3000 roundtrip C tickets they're leaving on the floor.