The inclusion of either a mid or post-credits scene (or hopefully both) is not going to be a surprise to anyone.
While his response does not specify whether both mid and post-credits scenes will be included, Gunn stresses that everyone should stay seated, barring a life and death scenario.
Now, that seems even more likely to be the case with a post-credits scene being confirmed.
However, if the post-credits scene does point to the larger picture of the MCU, Marvel Studios would likely allow Gunn to use the mid-credits scene for a fun beat that isn’t too important to the larger universe.