So how much longer will 4chan (and imageboards in general) will last? I’m going to guess about 6 more years till it implodes from Hiro’s horrid mismanagement of the site.
What are you talking about? 4chan has been dead for over a decade now. What you see here is a shambling corpse, not even a shadow of itself but a hollow being that badly tries to imitate it's former shadow.
Once 4chan died of cancer, 8chan was usable for a while, but with it's death that spelled the end for other imageboards as well. Webring tried and failed to bring that same magic, but all of these literally who sites are either dead or on life support now, including the 8chan skinwalker site ran by an open cuck and a pedo.
If you mean "when will 4chan die", I don't think the feds will allow that to happen. It is far too convenient as a honeypot to capture any potential problematic users and trap them into inaction by forcing them to argue with bots or retards instead of doing something productive or reading up on something they do not approve of. Even if they start posting something that makes them worry, they have an army of tranny jannies to shut it down the instant things start getting out of control. 4chan already has a reputation, and you can even say the dreaded N word there(then get banned when a tranny sees it outside of /pol/), it's a perfect magnet for young and edgy easily impressionable kids or people who are getting a bit too redpilled for their own good and think they might find other free spirits there. They can be groomed into a schizo and/or a tranny by the current culture(or what passes for one, anyways) or at the very least kept on a leash, not like they have an alternative anyways. Anyone who knows what's up doesn't use the site anymore for any serious amount of time, and even at it's peak it was a waste of time anyways.
Only ones who aren't being fucked with are very niche discussion boards/threads, but they're dying off too, discord and social media is seeing to that. That leaves schizos, shitflingers, porn addicted trannies and easily impressionable little kids screeching into the void and swimming in an ocean of piss...forever, 4chan isn't going anywhere, but most of us left 4chan while the going was good.
Edit:
Here is a rather accurate picture summarizing the whole "history" aspect, altho it's a bit outdated as it assumes any webring board still has any traffic anymore. Feel free to edit as you see fit if you disagree
