hmmm, I don't think so. I don't think Bitcoin will become the world's reserve currency, but I think that USDT or TUSD will be the world's reserve currency. USDT and TUSD have proven their price stability when the market is bearish like now, therefore I feel that one of the two coins is suitable to be the world's reserve currency...
Stablecoins are pegged to the USD. This means, that the reserve currency is the USD instead of a specific stablecoin. As for me, I don't trust stablecoins anymore since they've gone way below the promised value of 1 USD. The term "stablecoin" is just a niche to make believe that it'll never go below the 1 USD mark. But, it's nearly impossible to achieve considering that stablecoins are traded in the free market, where it's prone to either higher or lower prices by their traders.
If at some point in the future, the USD fails, then another currency might take its place as the reserve currency of the world. Considering how many banks and governments worldwide have been researching about blockchain technology, the reserve currency of the future might be issued either on its own blockchain or an already established blockchain. If they take the path of an established blockchain, then they'll choose the XRP Ledger since it's centralized and regulatory compliant.
Then, it could be the USD, EURO, YEN, or YUAN issued on the XRP Ledger for quick settlements around the world at cheap costs. For the reserve currency to be used all around the world, it would need to be implemented into a blockchain network. However, decentralized cryptocurrencies like Bitcoin and Ethereum would never become a reserve currency because of previously stated factors. A centralized cryptocurrrency would better serve a purpose of a reserve currency, and XRP fits the bill nicely. Just my opinion