4 bridges does sound nice, but the only one that I know of with a possibility of being built is one and associated roadways connecting the Intercounty Connector toll road in Maryland with Route 28 in Virginia.
Do you know off-hand what percent of Beltway traffic is I-95/270 through traffic? It would make sense to build a western bridge for the I-270 traffic and upgrade the eastern US 301 bridge to make it a bypass only if a fairly large percent of Beltway vehicle are just passing through the DC metro area.
28 to the ICE wouldn’t be bad.
I don’t ever want to see ever a Leesburg - Poolesville bridge. Love White’s Ferry.