What is not clear is what actually happens after that date.
My understanding is that you will not be able to submit a new release, but they don't tell the app will be blocked. So I fear it is case B. That's how I interpreted, to be on the safe side.
if you can't provide a new build yet
In fact, there is no need to develop a new version. You can simply re-archive the former version of the app with incremented build and version numbers, complete age ratings information and then submit with this "new" build.
In the what's new field of AppStoreConnect, simply say: minor bug fixes.
Given the many times this question is raised on the forum and how much it worries developers, it would be great to have a comprehensive answer from Apple.
Topic:
App Store Distribution & Marketing
SubTopic:
General