Google knows all..

[Brett]

I got curious whether Audi had made any progress in bringing a TDI model
to US shores, and typed in:
"Audi US"

Google's suggest feature finished the thought for me, tacking on "diesel".

Any guesses as to how hideously expensive the A4 3.0 TDI will be, or what
transmission options it'll have?

Looks like it's been pushed up (again) to mid 2009...

http://www.nytimes.com/2007/10/24/automobiles/autospecial/24audi.html

...or maybe not at all:
http://www.autobloggreen.com/2008/04/05/first-drive-2008-audi-a4-3-0-tdi-quattro/

Gas prices are at an all-time high, GM and Ford are seeing SUV sales
plummet so the market has clearly shifted, the R10 impressed many on the
ALMS circuit...and Audi management is too busy sitting on their hands,
playing it "safe" and trotting out the never-ending excuses that US buyers
are too stupid to want a TDI, despite VW's successes.

Brett