Wei Leping of MIIT predicts, "In 2020, the country will reach 600,000 to 800,000 base stations deployed." Given the early results of 5G 2.5 and 3.5 GHz radios, I estimate 5G will cover at least 500,000,000 people and probably many more. The main areas of the largest 50 cities will be covered.
5G phone prices will drop toward US$300 in 2020 according to both Huawei and China Mobile. The gap between 4G phones and 5G phones will drop toward US$50 or less. At those prices, it's reasonable to expect that many of the 300,000,000+ phones sold in China in 2020 will be 5G.
This estimate of 5G expansion may be low. Minister Miao Wei has urged the companies to accelerate. Wei Leping also projected 80,000 to 100,000 for 2019. Nomura's expectation for 2019 is 172,000, which seems more likely based on the limited information available.
The entry of China Broadcasting into 5G will also spur the telcos to go quickly.