All depends on the bredth the of the changes. FC have already hinted that (on Siptah) adds are being made to areas players currently cannot be built on so therefore not going to affect current builds. I am taking it as granted that there is a chance of issues and that bases near to the edge of the Maelstrom and close to the southern shoreline that may be affected.
Some people have put in thousands of hours of build over the years. Many of these players have known planned and unplanned wipes. It’s a thing. It can happen. I do hope that Funcom announce formally should Official server need to be wiped, but for extra content and land - I would be happy either way.
On Private servers, well, backups should always be done before ANY update either way (and a copy stored locally). As an Admin, UI would warm my players ahead of time of the likelihood of a Wipe so they can plan. If I were to Wipe, I would think of a way to fairly allow existing players to regain some stuff that they had (weapons, pets, t4 thralls, etc.), but I would also try to build it into the game by making it a shared disaster and then also add some content here and there to reward those that go looking for it.
I have put in nearly 6k hours into the game (split between Exiled Lands and Siptah) and have experienced many wipes, official and not. Depends on how much one enjoys a game. Rebuilding can be a lot of fun too, especially if you covet someone else’s base location. I would scout about before the Update so that if there’s a Wipe I’d already know where I will make a claim run