I think they'd rather go down in flames, come November, with the Messiah Obama than risk alienating the black electorate permanently by shunting him aside for Hillary, who could probably beat McCain in the general election. And I don't think a Michelle Obama "whitey" tape will change that, either!
See my 17.
I think you are right. The superdelegates are also concerned with the local and state elections in which heavy Black turnout is vital to getting their Congresscritters back in office, etc. The Presidency is nice, but their own continuance in power is their first priority.