It will take a few more years, but the delivery of packages via drone "has taken off" and what happens next is going to be predictable. You don't have to tip the drone! And, depending on the weight of a package, you won't need as many trucks and drivers. UPS understands this, that is why they have their own drone delivery development process underway.
But for today there is this news,
FAA approves drone delivery for Google spinoff Wing. I do find it interesting that Google beat Amazon to the punch with their first-in-the-nation package delivery approval by the FAA.
See this
NBC News item on the above story that illustrates the Google solution to the "last 25 feet" for deliveries.
Steve Myers shared the first link above.
Eric Holdeman is a contributing writer for Emergency Management magazine and is the former director of the King County, Wash., Office of Emergency Management.