I think hybrid cars will be able to develop more than diesel.
What is a hybrid? It's just a big application of electrical technology mixed with an ICE. The electrical component of a hybrid system can benefit from developments in other industries, such as the computer industry - how much research has been spent there, that has indirectly benefited the development of hybrid cars - heaps I would think.

And anyone thinking that power from a wall is dirty - well, all the processes for creating fuel are inherently dirty as well.