Without access to all the data, it is hard to judge the Clinton campaign’s call. Recall that John Kerry waited until the next morning to concede to George W. Bush in 2004, until the Ohio result was clear.
The additional twist now is that if the margin in a key state is within tens of thousands of votes in some of these states, there’s the likelihood that Clinton picks up a lot of votes that come in later through provisionals and absentee ballots. Whether it would be enough is the big question.
We will have a much better sense in the morning, and no one wants to be the next Al Gore.
But the most likely outcome now is a Clinton concession in the morning tomorrow.
(As to whether Clinton is being like Trump (who was roundly criticized) in failing to promise to concede upon losing, I’ve said repeatedly that candidates should concede once it is clear they have no path to victory, and not when it is too close to call. Trump was not limiting his comments to a razor-thin election.)
Update: News reports say Clinton has conceded, at about 2:43 am Eastern.