This should serve them well for the next 20 years.
http://fortune.com/2017/10/24/mazda-internal-combustion-engine-fuel-efficiency/
Sounds like a type of ram jet technology.
The precision of fuel control to make HCCI work on the street must be really high with a gasoline engine. Typically diesel engines have a lot lower of an rpm range. It makes sense though that there is a move in this direction with the computer controls in modern vehicles.
It would be interesting if the future was HCCI hydrogen burning ICE instead of batteries the way we are thinking these days -- still would be carbon neutral and might actually be less resource intense.