I’ve not really heard people saying Ark would replace LN. I’ve always heard that the best use case for Ark was that each transaction could BE a channel without any of the delay or general liquidity problems that tend to come with it.

Basically that Ark makes a fantastic way to create giant channel generating hubs. And obviously if it’s not integrated into the rest of the LN ecosystem, it’s basically useless in isolation. Lightning is the glue that holds every one of these other systems together. Roy has a great article about that actually