I'd add several more years to that for the FAA approval process.Probably forty years at the current incremental pace for battery technology gaining 2-4% a year. Two significant unknowns:
1. Charging infrastructure
2. Some break through in energy storage tech. e.g. Solve hydrogen fuel cell thermal issues, solid state batteries, silicon super capacitor....
Based on the money going into #2; I think it will happen. Question is when.