Given the already-mentioned favourable operating profile of the motor car compared to your typical light aircraft, we will be waiting and waiting until long after EVs become accepted in the motor car. I guess battery energy densities will need to improve to about half the energy density of hydrocarbon before they get a decent look-in. That's a factor of about 22; that figure allows for some on board power plant weight reduction to be offset against battery weight.
What density improvements have batteries achieved since the introduction of say Nickel metal hydrides? About a factor of six I think, based on what model Lipo batteries are capable of. We are not near ready for the infrastructural cost of recharging either.
I would put money on it that electric will never compete with hydrocarbons in aircraft for at least 30 years. Also leave out distorting tax incentives. What I would bet on is that solar bioengineering will harness microbes to produce hydrocarbon feedstock much sooner, making AFO fuel the best solution especially when distribution costs are factored in.