Sanders may very well be the Democratic nominee. He’s in second place and Hillary may be indicted or otherwise put out to pasture.
Hillary probably isn't going to be the nominee. But Bernie almost certainly won't be. The Democrat National Committee simply won't abide a member of another party (in this case, Socialist) running on their ticket.
It would be akin to a Libertarian or a Conservative running on the Republican ticket.
Ain't gonna happen.