True. The lead time for substantive changes to ATC systems is ten to 20 years. Most likely, air taxis would not be fully integrated into the controlled air space which is used by commercial flights. Adapting existing systems to do that would break a lot of existing functionality. For example a flight information region at the moment might handle 10000 tracks, much less than would be required with fully autonomous light aircraft in the sky.
So you will have to create new volumes of controlled airspace specifically for taxis, but there will be inevitable crossover because you will have helicopters from police, media, etc operating in both domains. So you put mode-s transponders on your taxis, they have TCAS and ADSB. But now you have to filter those new ads-b tracks out of your ATC system at the point of entry, without filtering away the tracks you do need to see.
But consider airport terminal areas. You want to see the taxis here because they will pop up on primary radars causing needless conflict alerts. So the whole thing pushes you towards a single, integrated airspace with that long lead time.
