I just installed macOS Big Sur on my iMac, and I wanted to give you feedback. I will post here bug if I find any.
First test: I installed Big Sur over Catalina, so far VSCode (latest version) and PIO (latest stable) both work out of the box. I just had to reinstall Git from the Command Line Tool package, as
sudo xcode-select --install kept telling me that the servers are busy. The CLI tools package can be downloaded directly here.
I also tried to compile my ESP32/8266 projects, they all compiled and transfered to their respective platforms flawlessly.