What I didn't like about AC: Origins was they gave no context for anything. The trailer, the demo footage, and the post show footage was all just sandbox mischief making. That may be a good thing for long time AC players (not giving any story spoilers) but for people like me who never got hooked on the earlier games there was nothing really that interested me about that title other than the fact that Ancient Egypt is cool (thanks Stargate). Maybe once I see some story ill be more hype and consider it.
If you didn't get hooked by the series' overarching story when it was good (relatively speaking), you're not really gonna get hooked after the series jumped a pile of sharks and leap-of-faith'd off the rails; Still, two possibilities. Either they got it back on track and are intending to keep the spoilers contained, or they're still going for last-two-months-of-dev excuse plot, in which case sayin' nothing and de-emphasizing it as much as they can is a save throw. Rumors abound, but specifics are scarce.
As for specific ancestor story... well, it seems to be a classic "ancient-Egypt" story (fun fact: the late period of ancient Egypt ended on 332 BC, some 280 and change years before game takes place. The game happens in
Ptolemaic Egypt, but "ancient" sounds cooler to the devs, apparently) with "artistic freedom" on the setting (but let's not poke more holes here); 49BC was Cleopatra's reign, right before her fall from power, failed rebellion, and exile. Right before meeting Caesar too, so presumably, the Cleopatra vs Ptolemy fight will make the social background of the game, mixed with the mysterious "mystery" that's been mentioned in passing in the ancestor's backstory.
I got into the AC games for the setting, I stayed for the story, but after AC3, gotta be honest. If you're comin' in for the story, be it the ancestor's specifics or the game myth arc, you're probably gonna be disappointed. The entire draw of the game is shenanigans in a cool setting.