If I am reading this correctly:
Before January 31:
you can submit new app versions without updating the rating
but you should update the rating if you do
After January 31:
before you can submit the app, you must update the rating
You don't have to immediately push a new version, apps will not be removed or blocked.
It's only if you want to push a new version that you will then be stopped until you update the age rating.
I had an app that I 'Removed from Sale' months back - and I still got that notification too.
Topic:
App Store Distribution & Marketing
SubTopic:
General