You have seen that the book concluded its story but the next scene would (implicitly) happen around adult Twilight reading it. This means that the fans are up to open it again and revive those memories like they did for the first time. Plus, some newcomers have never seen it at all, so it wouldn´t be fair to put this gen to the void all of a sudden, not to mention that Luster Dawn represents one of the many undefined paths that we have yet to see or write about in the fanfics. The timeline keeps going.
In this thread, we simply continue the show discussion but the fans decide what to do next. Not only it will serve for looking in hindsight to past content brought for an entire decade (the 2010s) but also for discussing future content of this franchise.
No more tensions nor worries about gen 4 anymore, you can discuss it more calmly without any pressure.
Welcome to the 2020s with the post gen 4 era!
...and let´s read the book full of memories again, one more time...