Amazon ordered scripts for Season 2 to be prepared whilst work on Season 1 were going on, allowing production to begin immediately in the event of a greenlight being given. However, the coronavirus pandemic hugely disrupted the shooting of Season 1. Originally planned to run from September 2019 to May 2020, shooting was suspended in March. It did resume in September but was suspended again in November with some scenes still incomplete. Production on Season 1 resumed just a few days ago, meaning that the team could be shooting Season 2 material within a few weeks.
Amazon typically give two-season orders to their new shows as a way of getting ahead of production delays and minimising the gaps between seasons. Assuming Season 2 is not impacted by any interruptions, it should be possible to air (or start airing) Season 1 before the end of 2021, with Season 2 to follow approximately year later.
Season 1 is predominantly based on The Eye of the World, the first book in Robert Jordan's Wheel of Time sequence, as well as incorporating material from the prequel novel New Spring. Season 2 is expected to draw on the events of The Great Hunt, the second book in the series. However, there are fourteen books in the series and the TV show is unlikely to run for fourteen seasons, so there is a greater likelihood that future seasons will incorporate events and characters from multiple novels, whilst some storylines and characters will likely be dropped due to a lack of time to incorporate them.