I think only some useless altcoins will die.
Do you think all altcoins will die if bitcoin reach $100k?
I don't know what kind of aspect when said useless altcoin. Some of altcoin many kind of aspect like, economic, influencer, finance, tech and anything. all of them usefull when altcoin to apply one. when bitcoin reach 100k, no problem with altcoin, it will be followed.
Many of the altcoins that we have in cryptocurrency market are taking the advantage of bitcoin growth to move upwards too and therefore, I disagree with the idea that when bitcoin is growing other altcoins will died. We have many coins that are there to resolve some economic problems we are having currently and as such in future what happened to bitcoin may not really affect them.