Ubisoft still has plans for the heroine.
The developers of Assassin’s Creed Shadows not only presented a collaboration with Attack on Titan, but also reminded players of the heroine from one of the previous installments of the franchise.
Kassandra from Assassin’s Creed Odyssey has reappeared — in the game, she is represented as an Easter egg statue.
Assistant Game Director of Assassin's Creed Shadows, Simon Lemay-Comtois, explained in a conversation with the author of the YouTube channel JorRaptor:
We really wanted to see Kassandra in the game. And, yes, [according to the lore] at this stage she is immortal and could very well have appeared in Japan, so we decided to connect these dots. Without revealing details, I will say: we came up with a story about when she went to Japan. What did she do there? Obviously, she did much more than just leave things in a cave.
The developer also hinted that Kassandra arrived alone. Just like in AC Odyssey, she has "essentially a whole ship" and a crew.
Details have not yet been revealed, but the developers have a plan:
We have an explanation for why there is a statue of Kassandra in the cave, which Kassandra herself bought. We may reveal this later. We thought everything through — we didn’t just add Kassandra there for no reason. And this is not the last content related to the Isu [Precursors] that will appear in Assassin’s Creed Shadows.