I think the future is fully automated routing of parcels in a network. This is a way of solving the last mile problem for a particular kind of place, but it doesn't build an actual network. In that sense the transmission medium is less important than the standards that allow interchange.
It's an interesting thought. In just-in-time manufacturing, the contracts between supplier and consumer can already be onerous enough to make shipping parts by helicopter the Right Thing To Do if there's a delivery hold-up.
