I don't see bitcoin being replaced by any coin in the near future. The strong bubble already ended when the bitcoin's price fell from its peak to almost 50% down at 8k$. There isn't any coin with as much potential as of now, but still if I had to name one such coin, it would be ETH.
Most of the ICOs are hosted on ERC20 tokens and the rising popularity of ETH make it a suitable candidate for being the second best coin.
It is true price of bitcoin was fallen very high few months ago but the reality is that now again bitcoin price is very high and affordable so if you will buy bitcoin today and you will hold your bitcoin for more than your patience then it will get high again, market price of bitcoin has been increased almost 70% and it is 30k, so no coin can be able to replace bitcoin even not ETH, for me bitcoin is the best and it will remain the same forever, as the peak value of ETH is 50% Less than the original price of bitcoin.