Oh, and in order to have the 21M limit, you need protocol ossification, otherwise that limit can also be relaxed. Given that the limit is a social convention resting on social agreement, you really do need people to buy into the fact that a 21M limit is good. Give it three or four generations and all bets are off.
Discussion
There is risk in everything. Getting the entire Bitcoin community and culture to pivot away from its fundamental premise i see personally as less likely than finding a very large deposit of gold or a new technology to extract it more efficiently, or a trusted entity manipulating numbers you must depend on to understand total supply.
Yes, there is risk in everything, especially in a speculative asset such as money. We don't need someone telling us about total supply to know that the total supply is limited by God and not by social convention. Subjective valuation leading to exchange on the margins brings prices. You don't have to accept an "official" price, either. The actual physical exchange prices of gold frequently deviate from the Chicago and London prices. The subjectivist marginal revolution in economics did not come until 1871, yet gold was money for thousands of years prior to that understanding. Or if you prefer Smith's 1776 work, still, gold was money for thousands of years prior to that. It didn't require the understanding of the participants in order to work.