Cafritz is developing Riverdale Park Station on property that straddles the old DC-Laurel trolley right of way. The land used to be Calvert Homes, built as WWII surge housing by the National Capital Housing Authority to serve workers at the ERCO plant which built light aircraft during the war. Several sections of that right-of-way in College Park and Hyattsville have been turned into trails and, as seen in the rendering above, Cafritz will continue the trail across their property. Cafritz just announced that advance work on that will begin in the next two to six months.
The trail will run north-south, and on the site plan below is along an extended Rhode Island Avenue.
Here's a video (ad really) with more.
Update: The project will also include a new bridge over the railroad tracks. That has not been designed yet, but the designers note that they "will construct an urban table top over the bridge to incorporate architectural features and provide green space for pedestrians accessing the redeveloped site on foot or by bicycle."
South of there, there is a crossing at East West Highway, but that's a little rough. Queensbury Road is good, even if it is at grade. North, you either have to use the College Park Metro underpass (escalators and stairs, etc...) or go to Paint Branch Parkway. Perhaps this could lead to a connection/expansion to the Northeast Branch trail along Wells Run.