no update has ever deleted bases.

but if you want the new content dont explore too much of your worldmap. as explored parts wont get updated content anymore. for example if you explore the entire ashlands down south your map is done for when ashlands releases at the end of the year roughly.

with hildirs update next month the black forest will see some new dungeon additions so explored black forests wont have any of these.

hildir will have a new camp somewhere in the meadows aswell. if all your meadows biomes on the map are fully explored that wouldnt be good.