I'd have thought they'd use mild or full hybridization, or even just more advanced actually clean diesels, at least as a transition.
NOBODY will believe VW when they announce they've got a new, clean diesel. In addition, European countries are announcing future, across-the-board bans on diesels, because the soot they produce is so damaging to health and structures. There's no future in diesel cars, and spending any more money on developing a BETTER dead-end technology is foolish. You might as well tell Kodak to make a slightly cheaper film camera, as digital cameras loom large.