FFG has not informed us about which PODs they plan to release or in what order. However, so far all the wizards and priest PODs that has been released has been the orders/faiths from the core set. In the core set the faiths that players could follow was Sigmar, Shallya and Morr (the wizards were Bright, Celestial and Gray). FFG seems to alternate between releasing priest and wizard PODs. As Sigmar amnd Shallya already have PODs and the latest POD to be released was a wizard POD (celestial) it's a good bet that Morr is the next one in the line. Do not take this as truth though, these are my speculation and guesses.
When the next POD (which might be Morr) is released is harder. The previous PODs were released in the following months:
January - Sigmar
(March - Dreadfleet captains)
April - Bright Order
May - Shallya
October - Celestial Order
In the beginning they released PODs quite often, but after Shallya we had to wait for 5 months for the Celestial POD. Based on that, my guess is that the next POD release could be anywhere between 3-6 months after Celestial, so February to April if I have to guess. This is pure speculation on my part though. It could be longer (or there might not be a next POD).