2020 is the only year that we may not get 2 APs.
Every other year since 5e's inception we've gotten 2 APs. And we've gotten 3 setting books in a row - Eberron, Wildemount, and Theros.
With the anticipated Icewind Dale AP for Sept release, it only remains to be seen what the Nov release will be.
What are you counting as APs? If you don't count the anthology adventures then there's been one storyline per year since 2017 (2017 Tomb of Annihilation, 2018 were the Waterdeep adventures, and 2019 was Descent into Avernus).