My guess (and it is a guess) is that if the August 2020 is in any way real, it's probably based on a tentative delivery of the manuscript around the end of this year or early next. I don't know enough about Rothfuss's writing process to know what state the MS is in now is he's planning delivery by end of year - he could be revising a full draft, or have a many-times-revised partial draft.
I may be inferring too much from the podcast interview he did at the end of March, but he didn't sound like he was approaching any kind of milestone that he was excited about. I would guess (and again, it's a guess) that he still has a significant amount to write, or if he has a complete draft, it needs a lot of revising.
HBJ