Just look at the
Audi R10 TDI diesel, in racing. In '06 and '07, it won Le Mans championships in both 12- and 24-hour competitions. What was the main advantage? FE. Fewer pit stops to fuel = more time to win.
If I had to predict the next 5 years of a possible new vehicle cost-of-ownership (as a Joe Schmoe average American), I cannot predict or trust the powers-that-be that control fuel prices. Just check the garage: fuel prices are on the rise, again.
Plus, being "Green" has surpassed fad into a sense of cultural responsibility (for many). If a buyer can afford it, a new car will likely be "responsible".
At least, that's how I see it.
-RH77