I emailed Subaru USA a month or so back and asked about this. At the time, they said they had no timeline. One of the car magazines, I think, suggested a 2009 release for the 2010 model year.

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1992 300D 2.5T
1980 Euro 300D (sadly, sold)
1998 Jetta TDI, 132K "Rudy"
1974 Triumph TR6
1999 Saab 9-5 wagon (wife's)