If there is eventually a fork that allows Bitcoin to be calculated to 16 decimal places then the halvings can continue for an additional 100 years and still not exceed 21 million coins.
Discussion
Satoshis are the unit in software and are an integer, so this doesn’t really make sense. In order to continue you would need to increase the total number of satoshi in the system. This is basically a stock split and would be used incredibly difficult if not impossible to coordinate. Can you imagine? Tick tock next block.