As I understand it also. In theory, the superdelegates are supposed to replace a really bad candidate with a better one. So, one should expect them to vote to nominate Bernie Sanders. Unfortunately, I doubt they will do their duty.

Super delegates were set up to allow more delegates to be chosen from the voting party members. Super delegates are elected officials and elected party officials that would stop people from being elected to delegate slots if they were in the mix. For instance my senatorial district has a total of 7 national delegates and 3 super delegates, if not for the super delegate allocations we would have only the 7 national delegates. They have no other real purpose. Contrary to what the media would have you believe no delegate to nationals has been chosen yet, and they won't be until they are certified by their state conventions. While they may be pledged, until they sign in at the national convention, and vote in caucus at the national convention, nothing is in stone. Most delegates do vote as they are pledged but they are not required to.

I'd bet that, if they intervene to stop Biden, they'd do so in a way to replace him with someone other than Sanders. I think they'd prefer to lose again to Trump than to win with Bernie.

Part of it varies state to state