The Concept CS Coupe is confirmed to be the basis for the next BMW 8 Series.  According to BMW CCA columnist Bob Roemer in his July 2008 "Heard on the Strabe"column, BMW will be launching the new coupe as a two-door coupe/convertible and four-door coupe.

"BMW is working on three cars that are the basis for the next 8 Series.  Code-named GT2 (two-door coupe and convertible) and GT4 (four-door coupe) they are luxurious, lightweight models based on the Concept CS Coupe, the swoopy show car BMW introduced at the 2007 Shanghai auto show.  The word is the 8 Series will both pay tribute to and redefine the automotive concept of Grand Touring - and become BMW's new flagship series.  The design team leader is Benoit Jacob (the designer of the retro BMW M1 Concept), who joined BMW in 2004."

Source:  Bob Roemer, BMW CCA Roundel Magazine, July 2008

I presume it will be outrageously expensive and positively guzzle gasoline ... looks like BMW's timing for the 8 series introduction is perfect again!