I think that the answer is quite obvious. There isn't any guarantee for Bitcoin to maintain its place in the market forever. Even it is not certain that Bitcoin will continue to exist forever or not. No kind of currency guarantees you such thing. You should always be ready to see even Bitcoin being destroyed by another cryptocurrency in the future. Maybe it will be an altcoin which already exists like Ethereum, BNB etc.. Or maybe, some people will announce a brand new cryptocurrency project in the future. And it will be even more promising than Bitcoin. And after some time, it will manage to leave Bitcoin behind and capture its throne.
That's certainly true, mate. Nothing lasts forever. Bitcoin may still be the "King of Crypto" but it can lose that position if another contender with a better technology than Blockchain comes up in the future. We should be prepared for the worst by diversifying our investment into more than one cryptocurrency. As a matter of fact, any cryptocurrency which relies on Blockchain technology is called an "altcoin" simply because Bitcoin is the one cryptocurrency that started it all. The pioneer cryptocurrency (BTC) has first-mover advantage so it's unlikely it'll go away anytime soon.
Again, only a new cryptocurrency with a better tech than Blockchain will be able to take down Bitcoin's place as the #1 cryptocurrency in the world. Until that happens, Bitcoin will be the leading cryptocurrency of the market. Instead of focusing on Bitcoin's "replacement", we should focus on making use of crypto/Blockchain tech for our own benefit. Crypto is all about decentralizing money so that people can have an "escape route" from the current monetary system. As long as there's freedom, nothing else matters. Just my thoughts