I don't think the fans being close minded applies to all of the negative backlash though. I feel like compared to many artists, Steven Wilson has pretty much always (since PT got popular at least) had a fan base defending his music like no other. Even the albums that got lesser reception are usually held up as the pinnacle of what musicians should strive for, and I would say he has stayed away from a lot of criticism. I don't think all of it is blind fanboyism though. I don't think the ground he walks is holy, and he definitely has albums I don't consider near the classic status they have, but I do think that even on a bad day, he usually delivers an album that is at worst, a decent album. But there's only so long you can have that luck going before you have a miss fire.
The new album could be amazing but even if the general reception turns out lukewarm, it's not that bad for an artist who puts out an album every 2-3 years and generally hits. Just for me personally, I don't mind SW changing styles, I just feel that lately (more than before) his take on different music styles haven't been nearly as interesting as the bands that did it initially. There's definitely some fans who are close minded and just want him to write prog, but I have seen a lot of people who prefer the poppier SW side (trains, lazarus, Blackfield etc) who didn't like Permanating, not because of the style, because they just didn't like it.