Well, assuming that, at most, each new episode continues to take around 4 months each, this is how long it would take for 3, 4, and 5 seasons of 4 episodes each starting from this month when development of ep 6 begins:
3 Seasons, 12 Episodes
- 7 episodes remaining x 4 months = 28 months. 28 months from June 2020 = October 2022
4 Seasons, 16 Episodes
- 11 episodes remaining x 4 months = 44 months. 44 months from June 2020 = February 2024
5 Seasons, 20 Episodes
- 15 episodes remaining x 60 months = 60 months. 60 months from June 2020 = June 2025