3.5, 3.7 GHz 1800. 2100. 2300. maybe even 700 can work just like LAA. Qualcomm, Verizon, and AT&T testing convincingly shows that commercial quality broadband can be delivered today over unlicensed spectrum. The telcos are targeting the Wi-Fi bands and possibly 3.5-4.2 GHz.
The same technology can be used to recover spectrum in licensed bands like 1800 & 2100, Especially in rural areas, massive amounts of licensed spectrum lie fallow. It would be enough, for example, to deliver a true gigabit of rural broadband.
LAA (Licensed Assisted Access) uses a control channel in licensed spectrum. AT&T is rolling it out later this year. That uses a sliver of licensed spectrum as a control channel and connects in other bands for capacity. Qualcomm has a similar system called MultiFire that works for new entrants because it doesn't require licensed spectrum.
Columbia Professor and FCC CTO Henning Schulzrine, believes "All new spectrum would be shared." Circumstances and estimates vary, but sharing spectrum usually at least doubles capacity.