Iron Gate is preparing to release Valheim's new Hearth & Home update tomorrow at 3:00 PM CEST (which is 9:00 AM Eastern/noon Pacific). There's a new update and overview from the Valheim Twitter account with what to expect and to answer some player questions.
When the update launches, any existing worlds that you already have won't be lost. The new update won't even be as accessible right away if you've already explored every corner of your existing maps. The new content will be live, but if you want to start trying it out, you'll have to do things like drop any ingredients you have and pick them up again, or to explore entirely new areas in order to access most of it. Because everyone's progression looks a little different, there's a good chance there aren't unexplored areas for many, so the team's general advice is to start fresh. "For the best experience, we recommend you to start a new world when you have downloaded the update," the Twitter post reads.
Additionally, once you download the content, you need to be sure that you're okay with your world or character not working with older versions of the game. So if you're going to try out Hearth & Home, there is no going back. This is also where starting a new world seems like good advice. The other option is to learn how to back up your worlds, this way you can try things out and return if that suits you best.
The team also advises to remove your mods completely and then access the new content. You may have errors if certain mods conflict, but you should be able to eventually re-add them after the Hearth & Home update has been out a while, or when your modders update that their mods do work with the update.
The update will bring some significant changes to Valheim, and it seems that the team wants players to be prepared for some of the potential difficulties they may face and temper expectations to have a smoother launch by addressing these concerns in advance. When Valheim Hearth & Home releases, feedback will be key.