Then again, you did say there's room east of both GA Ave and Fort Totten. (which would they use, though?) AND that there MIGHT be room between Waterfront and Navy Yard... if which there is, then they could do runs between GA Ave/Fort Totten and Waterfront.
I would not hold your breath waiting for WMATA to insert pocket tracks at or near any existing station. I will also note WMATA does not need a pocket track to do a short turn run. Virtually ever location where there are crossovers can be used to turn trains.
Surface/elevated are another story? Please explain.
Because no digging would be involved, inserting a pocket track at a surface location is much easier
(Far as I know, the only true pocket tracks at surface or elevated are Fran-Spring's tail tracks (would become pocket if the line were extended and the center track kept, hinting at the continued usage of the station for turnbacks), and the D&G Junction layup track. Grosvenor's track is in a tunnel, and I don't know how much one could count the center tracks at WFC or NA as "pocket", nor what one would consider WFC's alignment... surface or not?)
If you take away the platforms at National Airport (C10) and West Falls Church (K06) you have a pocket track. As far as I am concerned both National Airport (C10) and West Falls Church (K06) are pocket tracks, West Falls Church (K06) is a surface station.
John