There is a great deal of development work going on with small modular petrol driven gensets as range extenders. The target is to make them compact, lightweight and vibration free. If successful there could be an alternative to heavy batteries for medium size cars.
Mazda MX30 is designed to have a rotary engined range extender along with its 100 mile battery range range.
Will we see range extender equipped vehicles in 3 years?
BMW led the way of course but the i3 engine was an adapted motorcycle engine, not one designed from the ground up for the purpose.