I hate speculating about the plot like this, because I'm usually right or very close on the mark. But here goes...
2.55 Part 2
-Begins with the Attack on Ishgard and the destruction of the dragon barrier allowing the Horde entry within the city confines.
-The Holy See, lacking the manpower and the readiness to deal with the loss of the barrier sends Aymeric as a delegate to gain the support of the allies from the Scions. Using Aphinaud's pull on the city-states, the WoL visits Ul'dah, Gridania and Limsa Lominsa to convene a delegation on Ishgard's recent plea for aid against the Horde.
-While the delegation is assembled, the crystal braves begin preparations for security leading back into the so-called leak and conspiracy shadowing Ul'dah. The Scions, being outside the influence of the Crystal Braves decide to assist. Though, ultimately fail to find evidence.
-The delegates of the City-States arrive in Ul'dah and begin their discussions with Ishgard. Ultimately leading to Ul'dah's Monetarists unwilling to involve themselves, the delegation concludes
-The stalemate in the government incises the Sultana, believing the inaction of the Monetarists might finally be the time to nullify the current government.
-Meanwhile, new evidence is brought to light on the Ul'dahn conspiracy - an assassination on the sultana before she nullifies the government is planned. The crystal braves and the Scions scramble to uncover the assassin and the ringleader.
-The secrets are revealed. F'hlaminn is the source of the leaks. Working as the bartender in the Stones and being able to hear all sorts of gossip from the Braves recalls her earlier days Ul'dah. Lolorito recruited F'hlaminn as a spy in exchange for information on how to bring back Niellefresne. Believing the possibility that Nielle may yet be saved, F'hlaminn began working for the one man she once attempted to overthrow, and now spends the next several years as a spy for Lolorito while raising Minfillia all the while. -The Crystal Braves begin searching for F'hlaminn in secret to prevent the assassination. If she is publicly revealed as a co-conspirator, her connections will lead back to the Scions.
-One of the treasures of Ul'dah, a goblet, is revealed to be the key to bringing Nielle back.
-The sultana's declaration is about to be made, the assassination attempt goes off and fails, F'hlaminn, disguised as Crystal Brave, is revealed to be the culprit and apprehended. The connections are revealed and the Brass Blades are summoned to arrest the Scions.
-The WoL and the Scions are forced to defend themselves and escape. The scions stay behind to cover Minfillia's escape with the WoL.
-The WoL, together with Minfillia, Tataru, return to the Rising Stones. Word passes quickly and the Adventurer's Guild is forced to disolve their relationship with the Scions. Aymeric, knowing the deeds and assistance of the WoL in the past assists Minfillia in finding refuge within Ishgard's walls until the events and accusations in Ul'dah are settled.
At this point... I'm unclear what sort of events will happen next. I'm not quite sure what sort of motivation will have Yugiri reveal herself. Nor do I know where the airship in the trailer or what the Ascian machinations will be this time around. Perhaps more plotting and discussion over Nabriales' death. I do feel like there's a number of events left after the events in Ul'dah that will need to be covered in order to clear the Scions and make it possible for players to travel to Ul'dah and the remaining city states for later events in the story or general gameplay. How that will all fall out, I'm not too certain. But the above stuff I'm... at least 80% sure will happen, but I could be way, way off.