Why don't you think they can coexist, play roles and be used in different use cases in the modern financial system?
I know many people hate XRP and altcoins because they are centralized, but if we are realistic and accept the truth. This world is centralized, centralized services will survive and not only that, we depend on them to survive. So there is no need to avoid or badmouth them all the time.
XRP and many altcoins like AVAX, SOL, LINK are providing a lot of practical applications for the financial and banking sector. So, contrary to you, I don't think they will disappear anytime soon, they will become more and more ingrained and play an important role in the modern financial system.
Bitcoin and all other cryptocurrencies will coexist, and they will play different important roles in the future economy.
Although the world is centralized, that's not a guarantee that centralized products and/or services will survive. Companies rise and fall over time, paving the way for others to take over. XRP is no exception. Especially when it's backed by a centralized entity. What if Ripple, Inc. (the company) goes bankrupt or experiences a government crackdown? Then it will be the end of XRP for good.
With Bitcoin, it's a different story. That's because there's no centralized entity or person behind it. Anyone can become part of the network and support it for as long as they want to. In other words, there's no single point of failure. You don't see BTC concentrated in the hands of a single corporation. Neither you see BTC nodes concentrated within a single region. Nodes are geographically-distributed around the world, while the circulating supply is in the hands of the people. It's almost impossible to shut it down. That's why I believe BTC will last, while XRP will fade away into oblivion. Bow should I know? The future is unpredictable, so expect the unexpected.