I think Cilia meant that instead of having 2 optional level cap dungeons like in previous expansions, they would instead include those dungeons as part of the story for an extended max level msq sequence.
Unfortunately I have some reason to believe this is not the case in that I may have identified one of the optional dungeons in the launch trailer. Like you, I would also love to be wrong about it, and hopefully its just the camera making things hard to decipher. But we should indeed temper our expectations on the gameplay front.
This is the dungeon in question. And yes it is a dungeon; solo instances dont have treasure chests, and there is too much activity in the background for it to be an overworld FATE (which also dont have treasure chests now that i think about it). The reason I feel it is optional is because they don't show trusts fighting/running alongside us as in the other probable dungeons. Again, hopefully just the camera.
But if not, it might be to that Omega 2.0 enemy from the benchmark, what Akademia Anyder was to Archaeotania in ShB.