Bitcoin is the strongest coin in cryptomarket so i dont see any reason for bitcoin to be defeated by any shitcoins. Its given that not all altcoins will succeed in the future because they dont have real project to offer for us.
As long as the bitcoins didn't mine all, it will stay at the top, but probably there is a high chance that it will be replaced not today but it will soon.
It will take more years before bitcoin to be mined, and of course if theres a new coin to be replaced bitcoin I think it must be more advance than bitcoin in order for that coin to win in this competition.