Lahabrea might not be dead. His aether was absorbed into Ascalon/the Eye but we're a little unsure of what happens there. Ascalon is technically "a blade of light" since it's made of pure aether but whereas we've killed high-ranking Ascians in a 2 step process (capture->kill) and Thordan tried to do it all in one step. Worth noting Ascalon persisted after Thordan's death, so it's likely to be the catalyst for his return a la Zantetsuken.
While we're on the subject of Ascians: Unukalhai is very obviously tied to the Ascians, though he denies it. A young child, friends with Urianger, who knows the mind of primals and they both continually mention Unukalhai will help us with "the fate of this very star" which is the exact wording Elidibus uses to Urianger at the end of 2.55. Robes and mask not withstanding, Unukalhai is the brightest star in the Serpens constellation (which is the snake-half of the Serpentarius constellation). It's worth noting that Unukalhai is a "double star" irl so it might be a nod that Unukalhai is an avatar for Elidibus. Another big clue is he has these gemstones which have been lost for thousands of years.
The new primals are dual aspected as jibini mentions (and Unukalhai as well), which leaves us with ice-thunder next though there aren't a whole lot of candidates in traditional FF summoning library (though if you told me Bismarck as going to be a wind primal I'd shrug it off, so there's hope). More interestingly and of import for all you Enkidu-birthers out there is that Unukalhai says they were summoned without Ascian involvement. Considering Unukalhai's dubious origins I'm not inclined to believe him 100%, especially considering Igeyorhm post Ravana and Lahabrea's dialogue in 2.3 about plating divine seeds in the North. Said Igeyorhm dialogue makes it seem like they want primals to be summoned to wake up the Warring Triad.
The Triad seem to be our main focus point for the patches to come, it looked like the Ascians, the Garleans, and the Heaven's Ward all wanted to get to the Triad Control and do something.
Someone asked how the knights were able to transform into their Primal forms so readily, and for that I don't have answer. It might be as simple as having the dragon blood within them (which would apply to almost all Ishgardians, assuming they have prayer to sustain them) but yeah, that's a pretty big plot hole right now. Maybe they're using the weapons of Thordan's knights as conduits, who knows we don't have enough info unfortunately.
Unrelated, I bet dragons are from the moon. Tiamat says that Midgardsormr came from amongst the stars with 7 eggs and Bahamut lived on the moon in FF4 so COME ON CONFIRMED. It doesn't make sense for dragons to have myth/legends given how they experience time. (Tiamat thought she was bringing Bahamut back from the dead) It would also make Midgardsormr's pact with Hydaelyn make more sense "yo let me live on you and i'll protect you ok"
Reptoids are a cross between a Southern Aldernard lizard beastmen and scalekin. I wonder if it's ancient Amalj'aa x Drake? The confirmation Ixali are chimeras made by the Allag was fucking ridiculous though. Not at all what I was expecting. inb4 all beastmen are chimeric creations
I don't remember what else I was going into, but I expect Warring Triad to begin to feature prominently in at least the "Elder Primal" quest line, and for Cid to appear in the "Alexander" quest line. Still have next to no idea on wtf the 24-man story will be though... and the main scenario seems to continue with Nidhogg.