After a bit of digging and some attention to learning the traffic lingo, the VDOT site turns up this in-depth site describing changes and studies for the transportation systems in NOVA by the year 2020.

The summary report has county and city links to detailed tables of changes and studies. The Western Transportation Corridor (WTC) is noted with "Western Trans. Corridor construct I-95 to VA/MD state line - (lanes now) 4 (lanes then) 2020"

It's getting late, so I'll be trying to correlate this "VA/MD state line" with information from the Maryland DOT site another time. I only mention it because there was substantial and effective resistance to a western Potomac bridge by the residents of Virginia and Maryland. I believe it would have been an extention of US 28 north, past Dulles Airport, to cross the Potomac, into some very swanky Maryland neighborhoods.

Links: WaPo Coverage, Sustainable Loudoun, and Coalition For Smarter Growth.

And I don't necessarily endorse any of those groups above.