This is certainly true of a certain generation. The younger troons however are much more likely to have been raised in an environment that was very toxic towards Harry Potter and JK Rowling from the start. Should be interesting to see how that all plays out the next decade
This is all anecdotal, but I see teens and early-twenties troons and allies in the Potter fandom all the time. They might tag their stuff with "fuck JKR" or claim they don't give her money (by pirating or buying second-hand), but they're still unwilling to let go of it and they still keep it culturally relevant by engaging with it. They have a thousand and one excuses as to why what they're doing isn't "damaging" or it's even activism (by making Sirius Black a pooner), but they're definitely not letting go of it. A lot of these people are absolutely going to watch the new show and talk about it online, even if they claim to pirate it. There's
already drama about that.
In my personal life, I know a lot of kids in their early teens that love Potter and have no problem paying money for merchandising, be it books, water bottles, notebooks, pins, backpacks, whatever. They always talk excitedly about it when they find out I like it too. I even knew a thirteen year old trans identified girl (she no longer identifies as trans, thank god) who was very into online discourse, but never once mentioned Rowling or her views when she was excitedly guessing my Hogwarts house.
On a more general sense, I still see a lot of Potter cake toppers and decorations in showcases, Potter events for children and corners of libraries dedicated entirely to Potter. I see more adults who think they're making a statement by not including Potter in their classroom's reading lists than kids unwilling to read it (or watch it) on their own.
In my corner of the world, at least, Potter is as relevant as ever, and younger generations don't seem to care about Rowling's views. Older kids I've known use "transphobia" as a punchline. I agree that only time will tell, but for now I'm inclined to agree with Mourning_Cloak.