5G rarely will need new cells, especially in mid-band 2.6 GHz bands. Very respected Huang Yuhang of China Mobile Research told the Huawei Chengdu event that CM will not need "to build lots of new sites for 5G or interfering with its existing LTE network. Its spectrum in the 2.6GHz band is sufficient to support both networks in a shared architecture."
Sprint in the US, which also has 160 MHz of 2.6 GHz spectrum, is getting excellent coverage of 5G despite dedicating half the band to 4G enhancement. Massive MIMO in mid-band is performing so well that 5G needs few more cells than 4G requires.
When 5G was defined as millimetre wave, the short reach meant many areas would need new cells. Then 3GPP redefined 5G to include almost any new system. Most notoriously, 4G TDD-LTE now is called 5G if a very modest software tweak is added, "5G NR." The software has a very limited effect on performance.
21 of the first 23 "5G" deployments are mid and low-band, with reach comparable to the 4G already in the network. Few new cells are required in the 2.6 GHz band. That's mostly true in the more common 3.5 GHz band, although the data is more limited.
Ronan Dunne of Verizon confirms the speed of the new "5G" is very close to 4G.