Deadline’s report from the September 2019 renewal of Big Brother 2020 noted there was no official word at the time about Celebrity Big Brother Season 3.
As we now know, Celebrity Big Brother was in indeed not on the 2020 calendar.
But the site did add this hint: “However, while not totally dead, all indications are that CBB will not be on the CBS calendar in 2020.
The spinoff was not a part of Chen Moonves’ new package with the network.”