I think if anywhere, i think it would be in Old Country, fitting with the predicted DC overhaul of the area. The fenced off area is just where they took down the grandstand, and they don't want people going in the water.
I don't really think there's enough room in lakefront for a whole coaster. Most likely would be the rolling thunder footprint or old country area, depending if they want it to be more like a compact invert coaster or a hyper coaster.