I'm not even too sure if the federal government legally *can* declare the land to be a new state - it doesn't *own* DC, the land has been ceded to the federal government for the purposes of establishing a seat of government. The government can choose to shrink its size, but that *does not* answer the question of what happens with said land next. Logically it should be returned to the state that ceded it in the first place, as it was the case with Virginia's land, except Maryland doesn't want it back.