I think its very tough to reach their place because BTC is the one of the best crypto currency in the world also they are holding 1st positions in them market based on this if we look at the market conditions then I think ETH have this chances to compare.
bitcoin can never be replaced because the first bitcoin is the first altcoin in the world and so many altcoins are trying to replace bitcoin but it can not all because the first altcoin bitcoin in the world and very strong though often decreased