As long as you have finished 8.3 SFP, then there's no spoilers within Becky's Reckoning Prologue, the cliffhanger for the ending of SFP in May only comes part of Becky's story at the end of the year or very early next year, it's not part of the prologue, but if you wish to wait, then you will get Triss and Shelly's POV of Becky's 18th within the last update and Becky's POV of her 18th on her story