Ok, so, I've seen some murmurings around DailyKos that if Bernie Sanders was poised to win the most delegates through primaries and caucuses then the superdelegates would unilaterally push down on the scales to give the nomination to Hillary Clinton.
Quite simply, this is not going to happen and it absolutely shouldn't.
Same as in 2008 (where there were many of the same concerns) the superdelegates will end up going with whoever wins the most delegates via the voters.
Pragmatically speaking, I suspect they know they have to because if they didn't then it would tear the Democratic Party apart. We already had a dismally low turnout of democratic voters in 2014, lowest since World War 2.
If, in 2016, the democratic base was told that their opinion had been overridden and made irrelevant, the psychological impact would be so catastrophic on election day 2016 that we would need to make up new words to describe it.
So, it's not going to happen because no one in the Democratic party would win if a superdelegate override of the voter nomination process was enacted and the ensuing fallout would take place.
With that said, I will say right now that any Hillary Clinton supporter who wants to hold this prospect over the head of anyone they are debating with is being nothing more than divisive and undemocratic and should be shamed accordingly whenever spotted.