With the patch notes for the most recent Test Server update to Just Survive came a teaser for in-place upgrading of base structures. There is currently no dates given for when this will be available just that it will be included in the next major content update with the addition of stone building.
As we've teased before, our next major content update is in development and will include Stone Construction. The larger update will also be looking at combat, raid, and loot balance, as well as introducing another often requested feature, which you can view below: