Could this happen? Would 45 dare?

[Ca Bob]

It's possible, if done in a Trumpian way, as in a subtle threat couched as a prediction of some future event. The way to handle such a surprise would be to confront him on it directly. It would be hard for him to hold onto documents with which to blackmail the United States, and it would subject him to further searches, but he might suggest (ever so subtly) that there could be critically important documents etc etc.

The one thing that people would find hard to believe is that Trump has important knowledge in his head that he could threaten to use, although it is not entirely impossible. Maybe he knows the names of half a dozen deeply embedded spies.

My guess would be that the intelligence agencies have been doing their best to modify procedures, change codes, and replace deep agents as best they can due to their suspicions about Trump.

The other possibility is that our intelligence agencies already know that Trump is untrustworthy, possibly has been a Russian asset, and in any case is entirely amoral, being the sociopath that he his, and being motivated by his need for personal grandiosity and revenge. They may already have evidence that he has sold or tried to trade secrets, but they cannot reveal this for obvious reasons.