One factor which may affect the viability of electric flight is taxation.
If taxation on Avgas was reduced to the same level as the tax on the electricity used to charge batteries, then the economics of electric aircraft would fall away.
Hybrid cars exploit the use of batteries to smooth out the peaks and troughs in energy demand in a car. This is not really possible in an aircraft (gliders excepted).
If significant proportions of aircraft and cars start to use untaxed electricity (or lowly taxed), then governments will find a way to tax them.
So, we have the situation where a Kg of Avgas has 50p of Avgas plus £1.30 tax. If this is replaced with 44 MJ of electricity costing 30p the real saving is only 20p plus a tax saving of £1.30. Thus the technology to deliver electric power is really a tax avoidance scheme and governments can quickly close these loopholes down.