Cant see it. We had 3 years of May promising (over a 100 times) that the UK would leave on the 31st March - then she reneged. Boris stood for election based on leaving on the 31st Oct 'do or die' - and he has consistently repeated that promise.Or he can say he has in good conscience done everything he could within the law to leave on the 31st but his hands are now tied by those too cowardly to go to the ballot box. It might even work.
If he does a May and reneged on that promise he is toast.