I think that delivery services will evolve, and we'll eventually have droids flying packages to our homes. The droid flies automatically to your address and is then controlled by a person to lower the package to the landing area (driveway, porch, etc.) It's then controlled to a set height and then automatically returns to the postal or UPS warehouse for the next delivery. The controllers spend their day landing packages and the rest of the flight is automated.
Most letter mail (bills, notices, etc.) will be electronically delivered - this is already changing at a large rate. I believe getting paper copies of bills will begin to cost you extra, which will accelerate the process of paperless billing.
At some point, we'll be asked to pay per service. Take garbage for example. I live outside of the town limits, so my garbage service is optional. I can take it to a collection area at no cost or I can have curbside pick-up once per week at about $15 per month. For an extra fee (don't remember the cost) the garbage guys will walk to my garbage can and roll it out to the street to empty it and then roll it back. Why not charge $50/year for curbside mail and another $100 for delivery to your door. If you live in an apartment and your mail is delivered to a bank of boxes, why should you pay the same as someone who has a mail slot on their kitchen door?
When I was growing up, we lived on a dirt road with two other houses, and each house had it's own mailbox on the side of the road. About 10 years ago, all of the boxes were moved to a "mail rail" at the end of the dirt road. It probably saves the USPS 5 minutes and 3/4 per mile per day. Multiply that over the country, and it's a big savings. Question is, which house in the neighborhood gets to have a bank of 100-200 mailboxes erected on their front lawn?