Now here is the question, what would happen if Satoshi Nakamoto withdraws all his Bitcoin.
If you mean selling Bitcoin for fiat, it means Satoshi put his identity and safety at risk. It'll leave trace for others (such as government agency) to discover his identity and maybe even tracking his location.
Research has it that he is responsible for the "mega whale wallet" massive transaction as at 2010 and suspected he hasn't gone off but tactically cashing out since 2019.
For part "but tactically cashing out since 2019", can your provide source or provide explanation about this suspicion?