According to this article from the Washington Business Journal, the DC Government is soliciting development proposals for two sites (one at the SW corner of 4th Street & E Street and the other at the SW corner of 6th Street & School Street). The 4th Street site is a vacant lot while the other houses a fire station. A new firehouse must be part of the design for one of the parcels, or in the vicinity of the sites. While there are no specifications of what must be built there besides the fire station, that area of the neighborhood is dominated by office buildings, so I would imagine whatever is proposed will be more of the same - unimaginative office buildings with a sandwich shop or drycleaners as ground-floor retail. However, there are several office buildings either under construction or vacant near the sites, including Patriots Plaza, Capitol View, and Constitution Center, so who knows when anything would get built on these sites. At least the 4th Street site could support a sit-down restaurant on the ground floor. There are hundreds, if not thousands of workers nearby - NASA is across the street, the new forensics lab will be built across the street, as well as other existing federal tenants nearby. There are also residents as close as a block away who are yearning for more retail options in the neighborhood.