Very saddened to learn of Pope Francis' passing. As I understand it, it is the tradition of Poste Vaticane to make "Sede Vacante" postage stamps for the "interregnum" period between papacies.
Most recently in 2013, after Pope Benedict XVI resigned, Poste Vaticane released various price and color versions of the Sede Vacante postage stamps (I believe the color and price determined the postage rate per destination):

I tried searching for any information about the upcoming 2025 Sede Vacante postage stamps. I haven't seen anything posted online yet, likely given the recency of these events. I figured a thread about them would be worthwhile as we await updates.