It's not that "a bitcoin" necessarily needs to go away, it just needs to be deprecated for day to day use.

As I understand it a satoshi is the "true unit of account" on the ledger anyway. Most people will never have anywhere close to 100M sats and that percentage will continue to trend down over time and into future generations. Most won't ever have 50M sats... most won't ever have 10M sats... etc. etc.