An acquaintance of mine in Germany made a very good living shooting cars, until the industry there turned to CGI; two years ago at Photokina I met him the first time and he was suffering, now he has closed his studio, laid off his staff.
CGI allows new things like ads for white cars to be done easily, but I guess its killer aspect is faster previews and fast turnaround times for changes. I do agree with my acquaintance that the ads look unrealistic, shadows are wrong, tire textures are wrong, speculars are not quite right, the whole images look harsh.
I wouldn't invest in a studio if it didn't pay off within a year or so. My acquaintance was doing some of his work at a specially constructed for-rent facility with turntables for the cars, which has since also shut down.