[mamelukesabre]

I disagree. A hybrid powertrain allows a smaller internal combustion engine for the same peak power output. That alone translates to a superior fuel economy figure.

Personally, I think the CV transmission is the next big thing. This transmission keeps an engine at constant RPMs. So an engine design can be optimized for only one speed. The use of a CV transmission with a small diesel engine and lightweight automobile construction should give us some amazing fuel economy figures. The next step after that would be hybrid tech. But there’s some research work to do before a compression ignition engine can be used in a hybrid powertrain.

[Does so]

"...I think the CV transmission is the next big thing..."

Popular Science just published about one for bicycles. There doesn't seem to be much reason to think it can't be used for cars.

BTW: Leonardo da Vinci drew up the prototype!