Originally posted by Zathabar:

Must?
No not if things go as they have been. Without doing anything the new content may only appear in unexplored ares. But I always draw folks attention to a nice mod called upgrade world that resets biomes and the good thing is: once you have used it you don't have to run with it permanently.
Basically I have used it a couple of times ot reset the same world with the tar pit then Ice cave updates no issues.