We see that's some of the cryptocurrencies ranking level are decreased such as dogecoin before it was ranked #4 but currently I think it doesn't listed even in top #10 ranking... So can bitcoin also decrease its rank in the future or it will remain #1 rank forever?.
We don't know. No one knows. Maybe?
BUT, what we know is, Bitcoin's value is NOT what defines a cryptocurrency as Bitcoin. If you're here for fiat, trade shitcoins. They're more volatile, and would you give more opportunities.
Plus this take, Bitcoin will win the war of attrition against ALL shitcoins.