I am not an OpenAI Staff.
There is a topic on OpenAI Help page about your question:
What happens to my GPTs if I cancel my subscription?
Update
I saw two posts about this topic.
A summary about it:
If a Plus subscription is canceled, custom GPTs remain accessible to other users. However, you cannot edit these GPTs after canceling your Plus subscription because the custom GPT edit page will no longer be visible to you. Nonetheless, users who have previously accessed or used your custom GPTs can continue using them.