It's a multi-media franchise at this point like star wars is. The books themselves are still selling strongly (the illustrated editions and the MinaLima Editions being the most recent offerings, not counting the spin-off books), and the announcement of a Quidditch game was met with excitement and cautious optimism. Then there's the next Lego game, which the word surrounding it, is supposed to be like The Skywalker Saga but done with the Harry Potter movies.
So, while the movie aspect is in decline, the rest is not. Kind of like Star Wars currently...It has hits on the small screen but its big screen presence is in decline.
I mean, no.
Look, I 100% agree with
@Whizbang Dustyboots on the basics- Fantastic Beasts has shown us, fairly conclusively, that there are pretty severe limits on this IP. Even the new WB show isn't a new show- it's just the book/movies, again, as a TV series! That's not confidence in expanding a rich IP, that's throwing in the towel. Imagine if this was, as you posit, Star Wars, and Disney said, "Eh, given the fan reaction to what we've been doing, we're just going to re-do the original trilogy." It's still a large and powerful brand, but it's fairly limited to the original source material.
But more importantly, this would be the same, IF George Lucas was still 100% in control of all things Star Wars, and IF George Lucas decided to become the figurehead of a incredibly controversial stance that was roiling the major markets for Star Wars, including taunting fans by reminding them that their money was going to support his cause.
Despite the fact that people that are terminally online are quite aware of the JK Rowling controversies, it still hasn't really stuck for a lot of people. And it's not getting smaller. That's going to be the issue- because she retains so much control, and because she is so inextricably linked, and because this issue is just getting bigger and more heated ... I wouldn't have any cautious optimism.
It's been easy for a lot of people to say, "Whatever, man. I don't care. Just let me play my games and read my books." But the more this impacts real life, as we are seeing, the less tenable that position is when you know that money that is being spent is going to hurt real people.