I think he’s almost certain to get Obama’s backing, FWIW.
If Obama endorses anyone other than Biden then Biden is done. And he's obviously not going to endorse Biden.
But here's the thing: Biden is trying to run as a third term of Obama, and Obama pretended to be a center-left guy. In the context of todays Dem party he's considered a far right person. Of course he's as commie as they are but he never admitted it and they do and so he fails the purity test. His endorsement may not carry as much weight as he thinks it might.
So he’s used to doing the backing into Obama who is the pitcher.