Will it kill Ethereum?
Haha! I seriously doubt it. There are already lots of platforms out there and Ethereum is the largest. As an analogy, you are trying to compare an ANT to a GIANT. Unless waves actually does something and has projects that are built on it (currently none worth noting), the Ethereum giant will crush the little Waves ant.
Why not? Maybe someday or tomorrow? we don't know actually, yes the ethereum platform is a big giant, but if waves have and make a good project and have good enough update- does something on has to project I am sure waves will crash the ethereum.