To make a long story short: both of the show’s creators are in agreement that the series could and should return.
If Zal Batmanglij words to Esquire are any indication, then we can likely expect plenty more stories set within the world of The OA in the foreseeable future.
Perhaps optimistically, the duo have already started to work through the “mathematics” of another season, with subsequent stories telling similar self-contained tales that serve a greater overarching narrative for the series as a whole.
Batmanglij and Brit Marling (who also headlines the series as the mysterious Prairie) designed the show with an enormous sense of mythology in mind to justify some of the wilder elements, and this has allowed them to work through their established lore in order to figure out avenues for future seasons.