How do you know ETH gas fees will be lower in near few months? I don't think it will happen soonTM, so I believe BNB's rise will go on in next couple of months. Even if they fix ETH gas fee problem it won't be near as BNB's low fees. People get tired over 100$ swaps so they switch out. ETH swap fees won't be 1$ anytime.
We where all waiting for the ETH 2.0 to launch because we all believed it will help in the high cost of transaction fee, but unfortunately it has been launched and yet no much effect, this would actually be the reason for the binance smart chain to keep getting more users because people won't want to pay so much high fees for transactions when they can pay less in other blockchain network. There are people who would still use eth no matter it's high fees.