The truly elite prospects are few and far between. For prospects of the mortal variety, standing in the prospect rankings can ebb and flow. Sometimes a player advances further and more quickly than anyone expected, or a former organizational darling struggles unexpectedly.
As 2019 closes and many teams start to think more publicly about 2020, there are, as usual, a number of prospects who have put themselves on the radar for the 2020 season. Most won't become Pete Alonso, who went from an interesting High-A slugger to Triple-A terror in 2018 and is going for the 50-homer mark in 2019. But many of these players will contribute to MLB teams at some point in 2020.
I've tried to find one interesting player of this type for each team. I did not cheat and go with any of the obvious elite talents. If I told you "Casey Mize and Luis Robert might be good players in 2020," the proper response would be "No duh, Szymborski."