I expect the delivery fleet of the future to look like an Amazon Locker on a self-driving e-bike trailer frame. You get a ping when your package is on your block, and use your phone to open your locker.
If costs get low enough, it might be possible to do multiple delivery attempts per day. Something like "your delivery device will be on your block at 7:00, 9:00, 12:00, 3:00, 6:00 and 8:00".
Or, more optimally, you would configure delivery windows and tell it when someone will be available and they schedule one or two delivery times in that window.
