Okay, so, okay - - - it's pretty frustrating to invest so much energy into a worldsave just to have all progress be reset when an epic update comes out.
I'd love to see the devs figure out a balanced way to bring items from one safe file to another. Perhaps this could be a mod.
I'm imagining an event where the player must collect their most prized possessions and depart the world to have their gear and hopefully their beloved elk come with them.
Teleporting as well as timey-wimey craziness from the temporal rifts already exist.
Since this would be based on the player's actual progression, I imagine this could occur closer to mid-game.
Alternatively the player could be prompted to bury a cache like a chest which they are then forced to prospect to locate in a newly generated world.
Multiplayer & Previously Generated Worlds could handle this by transferring the cache data on the client side and then generating the cache in a previously ungenerated chunk.
The cache could also generate in a dungeon or event building.