Earlier this year, Facebook gave us a TIP (Telecom Infra Project*) about what could come next for them at the infrastructure level. Most members of the project, starting with Intel, Nokia, SK Telecom, Deutsche Telekom, are also on board of Facebook's much wider Open Compute Project, which also claims top coopetitor Google.
Terragraph (WiGig WiFi on 60 GHz) proposes ultra efficient W-LAN coverage for dense urban areas. You only need a station every 200 to 250 m. Of course it doesn't provide seamless handover, but a 200 m radius allows you more mobility than your typical hotspot.
Project ARIES (Antenna Radio Integration for Efficiency in Spectrum - MIMO) is more into W-WAN for rural areas. It combines 96 antennas to manage 24 simultaneous data streams, and aims at over 100 bps / Hz compared to 71 in early trials.
Here too, for a fraction of the price of a standard infra...
Could Facebook become a non-2-to-5G MNO, or a player in the game of standards? Not so fast. But an even more competitive value aggregator, certainly.
*** "Introducing Facebook's new terrestrial connectivity systems — Terragraph and Project ARIES" (Facebook 20160414)