I don't think it will kill Ethereum, it just becomes another possibility to run transactions on.
It will become a competitor but it will not kill Ethereum.
There will never be a platform who will be going to kill ethereum. As far as I know that this is already declared that so many times by various platforms to compete with ethereum but they can't even surpass ethereum's mcap.
DOT is only getting short term traction that created the pump. i do believe if the DOT's bullish trend will be ending very soon too.