It looks like even adventure mode will have a new map.
Source
My Fairy could help make things a bit more simple and I guess the new map is how Toon Link gets unlocked.
Perfectly Nintendo wrote:This week (most likely on Thursday), Koei-Tecmo will reveal a brand new trailer for Hyrule Warriors Legends, via the official website. And as we suspected, we’re also going to get some brand new details from Famitsu. Indeed, the usual batch of weekly previews went live a few minutes ago, and confirms the magazine will have an article about Hyrule Warriors Legends this week.
First, a new feature called “My Fairy” will be revealed: it looks like players will be able to get fairy characters to help them, but it’s not entirely clear how it all works. Second, we will get details about a brand new map for the Adventure Mode. Unsurprisingly, it’s based on The Legend of Zelda: The Wind Waker, and the map is the Great Sea itself. Unfortunately, we do not know if it will feature any special gimmick or not.
Source
My Fairy could help make things a bit more simple and I guess the new map is how Toon Link gets unlocked.