Earlier quoted context omitted.
How would Python 2 end up removed from a container image?
If someone builds a container that is designed like this: FROM debian RUN do-x RUN install python2 and then someone changes do-x, if I understand, the layers below it get invalidated and all of a sudden install python2 fails. This is very bad design but very easy to replicate.
Older versions of debian that still support python2 will theoritically be around forever, and any codebase that absolutely needs them should always work.
(though I contend that, given that we've had 15 YEARS of warning that this was coming, such instances should be vanishingly rare and not under active development)