I'm pretty sure they made clear they were basically re-using AC assets outrightand putting this Origins spin on it.
Unless they really threw a bunch of technical glitches and BS at it I can't see where AC fans can go wrong here.
No, they aren't just reusing stuff. They said in a video that they expanded the city from AC and changed some things. The added Christmas theme is layered throughout too in the game.
The only thing they basically carried over was the battle/fighting system and only made slight changes from what I have read.