It's very uncertain for an Altcoin to overcome Bitcoin.
It's not rare but impossible, so far no altcoin succeeds and thousands of altcoins died including Bitcoin forks.
Because Bitcoin is the only cryptocurrency that is decentralized from network to development. The only altcoin comes closely to it is Monero, and you will fail to find other altcoins that can be decentralized.
There are many altcoins with their names as Bitcoin forks, but they died with time too.
How many Bitcoin forks are there?Altcoin blockchains are worse than Bitcoin blockchain in security too.
https://howmanyconfs.com/People if are smart enough, will never want to exchange the best (Bitcoin) to worst ones (altcoins).