I think Motability will continue as long as car ownership (inc leasing) remains the majority, obviously as it swings in other directions? Although I think all inc hire will be more likely as cheaper EVs come online, which would lend itself well to an organisation like Motability.
As for ordering a robotaxi to my door? Yes, in some instances. It would allow me to keep a tiny runaround for local trips, shopping etc and then have a robotaxi to take us plus our luggage to the cruise terminal and home again etc. As long as it is pence per mile as suggested!