I'd wait! I don't think Josh and Dave have announced if/when their book will be updated for 2021. In past years, it was ready before the start of the year. This year so much is changing that I wouldn't put much stock in any book, at least not at the moment.
If it's written, I'd buy it myself. We are toying with the idea of putting the information online because there is just no way to keep it up to date in print form. If you had bought a 2021 book in January for a trip in November, almost all of the information would be out of date with so many things changing. Probably a thousand things have changed in the last four months. I think the Unofficial Guide finally gave up themselves. It's possible that come later this year enough will have normalized that most of what's in the book is "true again," and a print copy is possible. But even then, Disney will move the Rise signups from 2pm to 1pm for example, which is both a small change and a monumental one.
So I think taking things online is the only viable path. I had actually been saying that for three to five years. But it would take a long time to port everything over and update it.
So to answer your question four months late, I'm not sure I'd expect a print version this year. Even if it was 100% accurate today, it would become less and less accurate every day. We could make a list of changes, but I don't know how many people are going to want to have a book in one hand and either a printout or a device handy next to them with the hundreds of things that are wrong/changed.
I have an inaugural copy of the book, but the thing that has kept me from purchasing subsequent versions is exactly what you mention - the speed with which things change. FWIW, I'd be willing to pay an annual "subscription" for access to an online database with the same material as the book that's continually being updated.