Hope it won't come.
Stupid idea.
A supercar that sounds like an A4 TDI? Brilliant
What is an R8 all about? Noise, sound, emotion, driving pleasure. Just what a diesel can't do as good as a petrol engine. The noise of a diesel is awful, even a big one like 420cdi or 35d. It revs till 4.500, whoa, and then power decreases and kills the power impression...
A diesel is perfect on a sedan, where the massive torque gives a great power and comfort.
But on a supercar, you want a thrilling noise, you want to rev the motor till the red zone, you want to feel like in a F1... A diesel is big and heavy, torquey. But no revving, no sporty noise, no real emotion. It's a crap for a supercar. I never would buy it.
Next episode: the R8 diesel Sportback?

Because you need 7 seats and a big boot on your supercar...
An RS4 diesel, I say why not. But an R8? No way, man.