No one is able to predict what will happen next year, let alone time frames like decades or centuries. So, no one knows, and no one can tell you if bitcoin will even exist after miners stop getting paid via freshly-mined bitcoins. Staunch bitcoiners like myself expect that transaction fees will be enough to incentivize miners to continue providing security to the network, but for that, the price of bitcoin in fiat terms needs to go up considerably so that transactions fees would also be a sufficient amount to replace bitcoin block subsidy. However, the problem with high transaction fees (in fiat terms, not in bitcoin units terms) is that the base layer will become almost unusable for people wanting to transfer tiny sums, forcing them to switch to something more economically reliable, for example, sidechains, layer 2 solutions like Lightning Network or even alternative blockchains. So, in the future people will conduct most, if not all, of their transactions outside the base layer (the Bitcoin blockchain), which naturally will result in such undesirable outcomes as a decrease in security, privacy, censorship-resistance, and decentralization. The Bitcoin network will remain robust and decentralized and will be used for settlements of large transactions, but these transactions will no longer be a representation of individuals exchanging with other individuals.