Bitcoin is NOT mathematically limited to twenty one million bitcoins.
I do not support raising the cap at this time but if we had overwhelming support like we did for Segwit we could raise the limit to any number we could dream up.
I would have no issue changing the code to allow a 1 bitcoin reward for every block forever... to ensure a strong distributed mining community.
I understand this must sound like blasphemy to the majority of the community but it irks me to see such a false statement about bitcoin repeated over and over again in every Bitcoin youtube video out there; there has to be a better way to phase it.
The game theory involving the total supply of bitcoin is a self supporting one where the people with the most skin in the game are the strongest against it, because the more money you get on BTC, the less you like the idea of your savings depreciating by the total supply being increased, this is why I can sleep tight, because I know that the people with the most say in the game (the big holders) are all against that idea.
Also most people get attracted to owning BTC because of the limited supply.
I really can't picture a realistic scenario where the change would happen. While possible, in practice we can say it's set in stone.