Our education department updates the CBK's once every 3 years after the outline for the new exam has been posted for the public to have. It would be too costly to publish a new book each time NIST creates a new version of a standard.
When in doubt, remember that our certifications are a reflection of the current industry. This link should answer your question. It publicly available via our website, so feel free to pass it on: https://www.isc2.org/Certifications/References.
The exams team always uses the most current version of a reference. Each item is reviewed before it is put on the exam and this includes validating the reference and making sure the most current version is used.
We do update this list once a year so please reference this if you have questions.
Thanks for the info regarding when to expect an exam outline change. So for this date (Dec 2020), it's safe to say that since there's no announcement in the CAP section of the ISC2 website of any change to the exam, the current exam version remains valid til at least late Spring. Correct?
When hearing conflicting information, it is best to seek out an authoritative source. In this case, https://www.isc2.org/certifications/References .