The first batch of cards is called Once Upon a Pyre and the trailer features a cloaked woman in heraldry sitting with thugs in a tavern.
I'm thinking Falka, are we thinking Falka?
I say Falka mostly because of her white hair and the tittle of the expansion, Falka both lusted after power and payed for it, by burning on a pyre, her story became a folk tale, something we often retell with the phrase: Once upon a time.
But, there are other elements that make me doubt that, firstly, she is wearing, what I believe to be, CDPR's depiction of an old Temerian Coat of Arms worn by crown princes up until the time of Falka's rebellion, thing is, Falka is a redanian princess, she did however, led a rebellion against the Temerian king and Lara Dorren's daughter, an ancestor of Ciri, who was his queen.
Another counterpoint, according to the books, Falka's rebellion was composed of Nobles and peasants alike, and she fashioned herself royalty, partying in the tavern was more of Renfri's thing.
TL:DR. I'm thinking Falka but there are somethings that make me doubt that.