I think BNB can't replace the Bitcoin for being the King of all coins and even ETH. No doubt that the BNB's potential is there and for being almost on top in the market and offers small gas fee compaired to Ethereum. Many people still choose bitcoin because it has been known for a long time. Companies, stablishment and others already use bitcoin or accepting BTC for their transactions.
Months ago, I taught BNB could replace the ETH in the second spot in largest market cap but we all also see that ETH still dominates all altcoins in the market, breaking the barrier of $3k. There's no doubt many of riches people and large companies will choice bitcoin due to its total decentralized in nature and being the founder of cryptocurrency, no one can replace it.