In an electronic age, all that will survive is the physical delivery of hard goods by parcel. Too bad for the USPS that it conceded its dominance in that business to FedEx and UPS decades ago.
Actually, USPS is much better and cheaper for parcel deliveries than UPS - I do some business via ebay and I know whereof I speak. Way fewer hassles and online postage systems make it an essential part of the mail-order model.
A lot of on-line vendors would be crippled without it, particularly the smaller ones.