It’s pretty much already here, at least the posts that are worthwhile - there are plenty of people cross-posting content, although most are avoiding linking directly to Reddit. I think that if an instance chooses to federate with Reddit, they’d be reducing the overall quality of their content. That being said, it’s mostly harmless in this context, as I can’t really see folks who already use the Fediverse signing up on Reddit as a result.

I’d be more worried about Reddit using federation to scrape content from the Fediverse (although not as worried as I am about Meta). One of the main reasons I post to the Fediverse rather than Reddit now is because I don’t want Spez making money off my content, and any additional audience Reddit would bring my content in exchange is of dubious quality at best.