A post on the Nats Message Board, which is pretty active, claims that a Williams/Cropp Press Conference might happen between 11 and 11:15 PM. Here's the link to listen to WTOP live.
UPDATE: WTOP now reporting news conference at 11 PM.
MORE: WTOP now reporting a deal reached, awaiting official announcement. I'm currently listening to laser hair removal commercials.
EVEN MORE: The Post has its story up on the deal, but with no real new details of the agreement. Thankfully, hair removal commercials are over.
MORE (SORT OF): WTOP played what sounded like a bite from Mayor Williams talking about the deal, but claim they don't have a live feed there. No details reported, other than private financing permitted and liability for failure to build the stadium is split evenly between MLB and DC.