Prediction: The electric car will go completely mainstream by 2025.

Not the mass of the battery, but rather when the cost of the car comes down, that they will take over. Diesel is becoming persona non grata in Europe now that governments realised their emissions are worse than claimed (thanks VW et alia). Other fuels, like propane and E85 are just niche markets. I cannot see manufacturers keeping up R&D in gasoline engines much longer....