I predict we’ll see the earliest commercial use of eVTOL air taxis before 2030.
These will be in niche situations to begin with: Short hops maybe over water obstacles such as bays, lakes, and sounds mostly to and from major airports.
If there’s charging at both ends these short hops, then charging speed and battery durability may offset a small amount of energy density in the battery requirements—thus allowing earlier practical application. That is, the aircraft can charge while passengers debark and embark.
As for regulatory approval, I believe there’s already movement in the direction of eVTOL aircraft, but I don’t follow this particularly at the moment.
There will be some pressure on air travel providers to embrace electric air taxis as automobile autonomy and robotaxis will cut into air travel a bit. Parking garages will see less demand so their rooftops offer the opportunity for landing air taxis.
Starting perhaps between 2030 and 2035 unless there are impediments, BEV tunnels and Hyperloops could begin to create competition that will keep the airlines on their toes.
After 2035 but possibly before (if there is a technology accelerator such as a major war), earth-to-earth passenger rocket travel will begin to offer another opportunity for eVTOL in ferrying passengers to off-shore space ports.
These may seem aggressive estimates, but remember that we are again in a period of accelerated innovation and commercialization thereof.
I think Lilium Jet is worth following:
Lilium Jet - The First Electric VTOL (eVTOL) Jet - Lilium