Most previously expected deployments before 2022 to be extremely modest. The highly respected NTT DOCOMO CTO in 2015 predicted little mmWave mobile before 2022-2023. That became the common wisdom among leading engineers despite the massive pr it would be sooner. At the Brooklyn 5G, he acknowledged advances have been made and he now expects sooner. Ted Rappaport is no longer the outlier on projected volume deployment. Nothing is certain yet, but many think Onoe is on target. 3GPP, under pressure from telcos, is cooperating.
3GPP, under pressure from telcos, is cooperating. They are expediting the ridiculously named "5G New Radio Non-standalone." That's mostly a 4G LTE system with some software tweaks and the ability to use mmWave as well as Wi-Fi spectrum. The existing LTE network will handle the hard stuff,
such as handovers when a car driving 60 mph rapidly crosses cells. Existing LTE will "control" the network; the extra spectrum will add more data capacity. Inoe in his 2016 presentation "5G Myths" dispelled any thoughts of shutting down LTE for a decade or more. That too has become common wisdom, so the telcos can depend on LTE for the control plan for many years.
"Non-standalone" will have additional capacity from the added spectrum, possibly 5 gigabits to 200-600 homes. Towers will generally transmit about a gigabit to 2-4 times as many. Unlike "New Radio" in 3.5 GHz spectrum, it's not "fake 5G." Careful thinkers call "Non-standalone" and "fixed 5G mmWave" Phase One.
Intel is promising mmWave chip samples later in 2017 for mobile. Qualcomm is similar. Both are expecting production chips in 2019. The first chips will almost certainly be power-hungry, hot, and require large batteries. Some will get to testing and perhaps early adopters in 2019, making 2020 for a wider deployment perhaps reasonable.
Verizon I believe has decided to go ahead with a ~$20B small cell network to cover 1/3rd to 1/2 of the U.S. between 2019 & 2022. Officially, all they promise is "commercial deployments of fixed wireless mmWave & 4G small cells in 2019." Mobile 5G will be added when ready. They already are going full speed ahead with the small cells. Equipment is in place in 11 cities and the official announcement will be very soon. The vendors (Ericsson, Nokia, Samsung) are all promising an easy and inexpensive upgrade to mmWave mobile.
Massive mobile capacity ~2020 is extremely encouraging to Verizon, who just had their worst quarter in 20 years. Verizon's entire business model is based on charging premium prices for a better network. T-Mobile's network is now so close to Verizon performance in most cities customers are going for the lower prices. That's an important reason Verizon is rushing; they need to maintain an image of superiority.
10,000+ engineers are working away but nothing is guaranteed.