It will never happen as same as what happen with Bitcoin and Ethereum.
During the year 2017 or 2018, lots of crypto enthusiasts mentioned about the flippening between bitcoin and Ethereum.
After all, what's happened?
If this succeeds, BNB will soon be the second ETH and people will be very interested in this. I personally believe that BNB will soon develop well and may pass ETH in the future. Currently, BNB is getting more attention from ETH and the value of ETH has not changed over the past 2 weeks.
Maybe I am wrong, but I believe that there is no chance to see flippening between ETH and BNB.