Originally posted by Know pain:

I'm not talking about a test branch, I'm asking about the final update. I've only explored about 10% of my world and built a base there waiting on the update.

A more explicit answer vs some of the above is that due to changes to the seed updater, there is a possibility that you would have a different experience with a new iteration of seeds post the update vs using your older seed map. No one can give you a more accurate set answer beyond that at this point, really. because your exploration is only a partial factor(ie what you've rendered) with regards to the changes(ie the world seed generator alterations.).

If you want to ensure then a post update mistlands experience that may satisfy your wants, simply make a new seed(or clone your current one with a new name) post update. Consider it then to be a portal world and either shift everything(sans pet resources) to the new world and start anew or keep it as a separate world to visit(which if you do not kill the bosses on the new seed means you'll only get the boar/neck events whilst you deal with the denizens of the mistlands.

However again, it may just be a wait and see sort of thing.

Good hunting to you.