Verizon & Korea are building. NTT DOCOMO & China Mobile close. Many others mostly holding back, doing little until 2021-2023.
2019 for mobile phones, Qualcomm promises, as TSMC ramps 7 nm process to produce the chips.
Latency will be 5-10 milliseconds to the cloud controller intelligence.
1-2 milliseconds will be measured from the tower to the phone, but that's meaningless until and unless intelligence moves to the edge. That's likely very rare for a decade because there's no apparent market for 1 ms. Most "use cases" are bogus according to experts in connected cars, virtual reality, and telemedicine. Gerhard Fettweis's Tactile Internet is inspiring but years or decades away most places.