BNB is a coin that is growing due to the growing popularity of the Binance exchange, due to the growing popularity of IEO, in order to participate in which it is necessary to acquire BNB. This project has nothing to do with Ethereum, so I believe that comparing them is not correct and BNB will not be able to kill Ethereum.
I am sure that BNB's performance can have a big impact on crypto markets, and now we can see that more and more projects are only relying on the IEO, and I am sure they can be like EOS and leave Ethereum.