How do I postpone an already postponed deletion
First an educated (wild) guess ... Since Drupal, out-of-the-box, does not come with some "postpone" facility, I'm going to assume that you implemented that by using the Rules Scheduler to schedule the execution of a Rules Component, which does nothing but delete some content (node).

Have a look at my answer to the question "How can I set a reminder for a specific user to be triggered on a specific date?". Obviously, that is not the same question as yours here. But the "specific date" there appears to correspond to your "postponed date".

With that, you could just trigger a rule each time that the content is edited, and then verify the relevant data of your content to decide if you need to do either of these:


no more need to postpone the deletion of content "later on", so just DELETE the scheduled execution of the Rule to delete content.
(re-)schedule the execution of the Rule to delete content.


PS: from revision 1 of your question, I understand it is about D7 ...