(A first sketch)The short range of high frequencies means you need slews of cell sites and massive backhaul. (Think every lamppost.) In most places only the incumbents have enough backhaul capacity. If we go widely for high frequencies, we will need to take drastic steps to maintain competition. More and more, it's looking like telecom is again tending toward monopoly. On the other hand, regulation has many problems. No easy answers here.
Certainly, mmWave is right for some places. The thousands of MHz little used in millimeter can deliver literally tens of gigabits of data. Ted Rappaport at NYU and now the telecom giants agree. As Ted says, "It will work!!!."
The U.S. FCC and the ITU World Radio Conference are allocating spectrum. I haven't met anyone who says the technology won't work. The question is whether millimeter wave networks will make sense to build. The costs of that many sites - with backhaul - is not sensible in many areas. High backhaul is why AT&T cut back on their small cell deployment plans.
Promotion in 5G is mostly about high frequencies. The telcos' plans for 5G is mostly below 6 GHz for years to come. Both AT&T and China Mobile have repeatedly emphasized how much more important it is to release spectrum below 6 GHz. NTT doesn't expect high frequency gear will be practical for seven years or more. NTT's presentation suggests it will take until 2019 or 2020 before the standards are set.
More interesting news gets more notice. New millimeter technology is more exciting than upgrades to what's already being done. Adding more sites is not exciting. Neither is going from 2 to 4 carrier bands, even if that more than doubles capacity. More bands (carrier aggregation), more cell sites (densification), more MIMO (4x4 and 8x8) and more WiFi upload (in countries like France) are what the carriers plan if they need capacity. More sites are very expensive; technology, like MIMO may be advancing fast enough to meet demand growth.
Demand growth is down by half in the last few years and Cisco predicts the trend will continue.
Note. A first sketch is something I wrote quickly to get the story out because I think it's important to get people thinking. A proper article on this one would be loaded with datapoints demonstrating what I'm suggesting. I'll write one if I ever get caught up but I never seem to get caught up. I'm also experimenting with adding "AO" to articles mostly analysis and opinion. There's much more that needs to be written