BTC is not only the first coin but it has symbolic value for the entire crypto market, one symbol of the blockchain revolution.
Just like gold, there are thousands of metals produced such as steel, aluminum, silver, etc., which are widely used in daily life. but gold has always been the most valuable metal, still number 1.
So there will be no altcoins that can replace BTC although ETH, Sol, Tron or Xrp... have utilities, applications and technologies that are far superior to BTC.
It depends on your preference, I believe there are Alt-Coins already replacing Bitcoin on some people's portfolio already, so people are selling of their BTC, or aren't buying BTC as to preference to Alt-Coins.
It always about the Crypto enthusiast choice, but right now generally Bitcoin has more holders , for now and things are fast changing, even if Bitcoin would still be relevant in the future some Alt-Coins would also be up there.