Lawrence O'Donnell has the scoop on what seems to me the most likely scenario for how this finally plays out:

[T]he Clinton campaign plan is to collect as many votes and delegates as they can right through June 3, then take no more than a week or so to make their case to the superdelegates. Nothing he said indicated that he actually expected the superdelegates to move to Hillary in the week after the final election. The Clinton campaign has not lost its grip on reality. Yes, Clinton spokespersons publicly seem to be lost on gravity-free planet Clinton, but privately they know the end is near.

Having come this far, and withstood for months now the critique that her campaign has been moving the goalposts, it doesn't seem too far a stretch to believe that with a mere 3 and a half weeks until the final votes are cast, Clinton will stay in. Since March, after all, her strategy has been primarily to be the person Democrats can turn to when the Obama locomotive goes off the rails. That strategy is running out of time, to be sure, but why not stick it out for one more month and see if it pans out?