Preview video here.
So, it looks like Mamool Ja have taken over. There is at least a Mamool Ja mid-boss seen around the 2 minute mark. Why is that important? Lets go back to E3 2013 for that;
SourceGE: In the last live letter, when you were showing off the chocobo companion, it looked like there were Mamool Ja in La Noscea. Were those Mamool Ja? Why they are in FFXIV and what role do they play?
Yoshida: Yes, they were Mamool Ja. One of the concepts in developing FFXIV is to bring the flavor of other Final Fantasy games. We have a lot of monsters from not just FFXI, but also FFXII and some from FFXIII and past games in the series as well. But that’s not to say we’re randomly picking monsters. They will all have their own back-story, so for example, for the Mamool Ja, there will be quests that will explain why the Mamool Ja are in Eorzea.
GE: In FFXI they were were one of the big beastmen races. Are they going to have a role similar to that in FFXIV?
Yoshida: No, their presence isn’t as large as the other beast tribes in Eorzea. But that doesn’t mean that over the next few patches and updates that they won’t develop a stronger presence in Eorzea and maybe getting strong enough to maybe summon, their own, maybe, primal, maybe.
Took them over a year, but the Mamool Ja are finally getting stronger, are we also getting a new Primal at the end of this dungeon? I doubt they'd put an actual Primal as a dungeon boss (lore wise I don't believe bosses like Fenrir are actually Primals), but we could be going there to prevent a summoning.
Do we currently have any lore on Mamool Ja? I imagine the dungeon will give us plenty, but other than their ritual dance and the fact that they are mercenaries I can't think of a lot... I could see them taking the lazy route and just making Gulool Ja Ja their Primal, but if we're going to have a two headed freak as a Primal, I'd rather see them summon Anima...
Also, while I doubt they're going this way with it;
"A Mysterious New Trial" could always end up being a Mamool Ja Primal fight. More likely it's just the Minstrels Ballad giving us a rematch with the Garlean Rangers though, given that idea has been tossed around so much.