it can literally be both especially if it's a long trailer.
Nomura specifically referenced Disney Properties and in many interviews Nomura specifies Disney Worlds as ones being traveled to via gummi ship so that in and of itself eliminates 100 Acre Wood from this discussion as that is not a world traveled to on Gummi Ship.
I'm not saying it does not count towards the final game count it absolutely does but it does not count with Nomura's quote because it is not journeyed to via gummi ship.
The Gummi Ship is returning in Kingdom Hearts 3, which I think is interesting. I'm curious why you decided to bring it back? What you think it can add to Kingdom Hearts 3. Is it to tie it more into the previous games?
Nomura: "In Kingdom Hearts numbered titles, the Gummi Ship has always been there to travel between the worlds. Gummi Ships are part of the basics of Kingdom Hearts, and as a numbered title in the series, I thought it was necessary to have it in there to complete the package. This is something that [Hironobu Sakaguchi] told me once, which is that Final Fantasy is a title that just has everything in it.
I wanted to bring that to Kingdom Hearts. In Kingdom Hearts there's the shooting game, there's the RPG, there's the adventure game. It has action, command battles, and everything. There's customization with Gummi Ships, and they bring with them the shooter aspect and the travel aspect. It's just a part of Kingdom Hearts. That's why I thought it was necessary to have it in the title".
https://www.usgamer.net/articles/tetsuya-nomura-kingdom-hearts-3-interview
So I mean that to me suggests the Disney Worlds that are part of the 3 that each team worked on are worlds travelled to via gummi ship, not a sub world in an original world which is 100 Acre Wood.
Like I said though on December 10th we'll know cause they already said when all the Disney Worlds are revealed they'll announce as such. If they don't reveal on Dec 10th that such and such is the last world then the final Disney World will be revealed in December 18th in the story trailer.