One big reason that imageboards are not going to be making a comeback is due to the changed nature of the online ecosystem. The internet has been changed - permanently marred, really - by the sheer prevalence of social media. In 4chan's time, if you had beef with a given community or even another imageboard, you just didn't need to fucking go there and maybe talk about it and that was the fucking end of it.
Nowadays we have entire groups who literally do nothing but hunt down opinions they don't like and push towards getting them removed from the internet writ large. We have people online - quite literal human detritus like
Bardfinn - who literally will go to a community that's done no wrong except express an opinion he personally disapproves of - and actively go out of his way to sabotage it. by literally uploading child porn to it - and individuals like Bardfinn are
terrifyingly common as jannies within the operating of the modern internet now. They quite literally think anything they do to fuck with you is fair game, lest your opinion and not theirs reach the mainstream consciousness. The mere fact that you exist and express an opinion other than theirs is an offense they cannot countenance, because every waking second that opinion exists out there, unmolested and unfiltered, is a reminder of how fucking worthless shitheads like this are.
There is no restraint in their actions: If they could murder you over even tangential disagreement with their doctrine, they would do it with an honest-to-god smile on their faces.
Of course, anyone with a passing understanding of cause and effect sees the problem here: Namely that the jannies themselves are a literal advertisement against their own positions, and that the Streisand Effect remains alive and well. Reddit didn't get its reputation as the most toxic and malicious shithole on the internet in a vacuum; the shitheads running it made it that way. There are so many cows we cover that are also the literal embodiment of why everyone considers Jannies the lowest form of online social life that it is practically a meme, and they have done, through their hubris, more damage to their own side than all of us combined shitposting with the force of a thermobaric warhead could. Every single day reality refuses to conform to the delusion is more salt in the wounds.
Therein lies why we aren't going to see image boards return as a mainline form of internet content for some time. Not until this current crop of online faggotry starts to die off (figuratively, and we're slowly edging that direction) at least. The anonymous nature of them makes fucking with them pretty much effortless, and there are defective people with nothing but free time who will do nothing but camp a board waiting for the perfect time to act like a fucker and then self-report it to daddy government and every friendly journalist outlet they can reach. They don't care that it makes tjhings worse for everyone, they view any transgression from their orthodoxy as apostasy and they will act accordingly. They used this tactic to destroy 8chan (8chan's userbase being fucking retarded did it no favors, but the gay ops done to destroy it are undeniable), they've used it against subreddits they don't like, and they've used it to shut forums down.
......But there will come a time when this shit winds down. The troons and loons who actively make online discourse worse have long since outlived their usefulness to the establishment, and their chronic health problems and embrace of vice and weakness means they will essentially burn themselves out, either figuratively or literally. On the global stage, the tide has turned against them - the UK (of all places) literally just dropped the legal YWNBAW in their laps, and the very nature of their breed of activism means they will exhaust themselves in their bloodlust long before we all collectively stop being shatteringly autistic. Once the dust settles from that, you're going to see a return of imageboard culture, though it will take a different form from how it was in our time. I personally look forward to seeing it.