I'm sorry to go back but I didn't get a chance to comment on this before. I really don't think the end of the current DCEU is going to have any effect on the upcoming movies. Like other people have said, the interconnected universe is fun, but for the majority of people, I really don't think it's going effect whether they see it or not. I think for most people, myself included, it's secondary to just seeing a movie I enjoy. I do see every Marvel movie, but not because they're all connected, but just because I enjoy the movies. If there was one that really just didn't interest me, then I would happily skip it.
While I am disappointed that Gunn appears to be getting rid of the current actors, I can completely understand why he would be doing it. They brought him in the do his own thing, and so I can see him wanting to bring in new actors that fit what he is planning better than who we had before.