Don't hold your breath on Raptor meeting its design goals. They have done some amazing stuff building their prototype but they are out of their depth when it comes to engineering and developing stuff, demonstrated amply by the way they've missed their empty weight by, what, over 600lb? That's not even weighing a completed airframe yet. I reckon it'll be even more than that by the time it's test flight ready.
The state-of-the-art in diesel aero engines is already out there and it's too expensive and heavy but under some circumstances it works. The DA42 is where it works well enough to be useful but it's not a game changer.