Sullivan can easily file a request for an en banc rehearing. That would kick the can down the road another month before it is denied - if it is denied - a few months otherwise.
I was thinking even if the case is over and the gag order lifted, Flynn may not talk due to threats from the deep state.
I think he would also have to request a stay of the order to dismiss. This could still get more complicated. If Sullivan follows the order then further litigation would seem to be moot. Would a higher court order the REVERSAL of a dismissal requested by the prosecution? Seems unlikely.