The courts can make anything happen .

He's a vindictive little man, even if he is stuck with Twitter at the price he paid, he probably wants revenge. Any evidence about information he didn't see will be fair game to claim witholding information from the court. And maybe a sec fraud indictment against those that were at the helm of Twitter.

He wouldn't be able to change the deal, but a lawsuit against the previous board/executives is possible.

The entire waiving of due diligence thing is also such a weird talking point. There was no contingency on due diligence, but part of the deal did include access to the information he would need to do it and any incorrect information in public filings should have been enough to get out of the deal.