They are indeed a rival, but if Listed BNB token would bring and atrract more people to come and trade on Kucoin, who doesn't want that? As we know too if BNB token is one of superior token which their value has increased multiple times just on this year.
Now for Kucoin to go onto BNB... Seems unlikely though
Anything could happen man
Kucoin is too small compared to binance. Binance won't even think that they are their competitor. There are many shitcoins listed on the platform. If they can list shitcoins then they might list a good coin which has a decent amount of trading volume.