Some things we know, and some speculation
The central conflict seems to center around the races of XC1 forming the country of Keves (Mechanically focused), and the XC2 races formed Angus (Ether Focused). 3 party members from each side, we have a Homs, a Machina, a Part-High Entia, a Gormotti Flesh Eater, a Full Blade, and another human character of unclear origin. There's an etching in the 3 in the logo, and the etching is on all the members of Keves: Noah's right hand, Eunie's chest, and Lanz's chin. There's also a half-circle on the weapons and tech of each side, and they're complementary, forming two halves. Mechanically, we're looking at the return of item orbs, 4 character parties, no Gacha, and an expansion of traversal. We know of the boat, and its implied there's a diving mechanic in any place in the water? should be interesting
If I were to make guesses about themes, the main characters are off-seers of the dead, and we could see a game about life and death, and its inevitability. There's potential for previous characters to return (those that can live hundreds of years) and the death and life theme could be contrasted by those in faux immortality. War is an easy one, and obviously we'll see more Takahashi philosophy as every game does. What's notable about this game is that there's quite a good amount of politics right out of the gate, something we haven't seen in any of the mainline Blade games. Should be neat.
There's a lot of other things, but this is what I've been able to put together
In other news, I'm very excited