Lots and lots of small changes to enhance the core gameplay is the theme of this update. It expands the game a little on all fronts instead of adding a big, noticeable new area to explore. One thing is that some of the new content becomes available only after certain things are done first, like what Odyssey is referring to. And there are a few of these so it's about playing as you usually do but getting a little more at every turn, including during later gameplay so that will be revealed as you continue playing.
Not only late game changes, but changes throughout the game including some that are only accessible later in the game. However if you bring up a later game save, most of the things will happen more quickly because you've 'unlocked' many of the prerequisites during the course of your previous gameplay. I can't think of anything specific that you would completely miss by opening up an older save but that's just because I mostly forget everything.
