According to Musk, Walter Isaacson has already starting writing.
If you’re curious about Tesla, SpaceX & my general goings on, @WalterIsaacson is writing a biography
— Elon Musk (@elonmusk) August 5, 2021
My take: Shrewd choice, for both subject and writer. I know Walter pretty well. He’s fast and thorough and his Musk biography is likely to be definitive.