M Street SE, from the waterfront to the Navy Yard, is included in the "high priority corridors" in the DC Metro system's 10-year expansion plan for light rail or bus rapid transit. Two corridors--from the Anacostia Corridor to the Waterfront Metro station, and from the Silver Spring Metro station to Anacostia--would run along M Street. A three-mile demonstration version will be built in Anacostia in 2004.
One of the "landmarks" of the old M Street disappeared at some point in the last month--the boarded up gas station on the northwest corner of 3rd and M. Eventually there will be another office building there (250 M Street), but there's no firm construction date yet ("maybe in 2004", according to a William C. Smith rep). (May 2004 update: fences have gone up around the lot, but not for construction--it's been turned into a parking lot, so it doesn't look like they're planning for development anytime soon.)