The National Capital Planning Commission and the D.C. Office of Planning have been studying the impacts of raising D.C.'s height limits. Recently, DCOP released a series of renderings showing what D.C. would look like if the height limit was raised.
Check them out
here, but consider that it's likely that not all buildings would rise to exactly the tallest height allowed. D.C. Office of Planning director Harriet Tregoning said in a discussion (
quoted on Twitter) that the models represent "worst-case scenarios."