Is it possible that the sac event might directly follow this current event and therefore give everyone double the chance of a 4 or 5* toon before the week runs out? That way it's a double win!
It may only be both for a day or two but I would be pretty sure everyone will have sacrificed all their saved souls in that time....
I have more than 1200 regular souls and approx 200 rare or better souls to throw in the book of souls, if I'm right it will hopefully be a fruitful next couple of days...