Originally posted by Flamekeeper:

I believe I heard they're adding some things to the plains but don't quote me on that

Das is true, as to what though the developers did not say as to keep it fun for us to find out.

Referring to the op, developers said biomes are being later brought in as giving a new boss and enemies would majorly upset what they already have and is why they have spent this update getting all the foundations ready for new enemies and bosses.