I do not believe that a time will come when bitcoin will be overtaken by another cryptocurrencies.  Considering the many factors that contributes to the success of bitcoin as the number one cryptocurrency, you'd realise that no other cryptocurrencies comes close.
If you'd talk in terms of price, bitcoin tops the list. The second cryptocurrency is Ethereum and it just surpassed the $4k mark unlike bitcoin that has a ATH of $63k.
Secondly, talking about adoption, bitcoin has gain widespread adoption more than any other cryptocurrency. This is partially due to the fact that it is the first cryptocurrency and partially due to the fact that quite a lot of top companies are adopting it.