Sanders people are getting too hung up on warren. The signs have always been there that she's very party conscious, not the firebrand progressives thought she was going to be. Bernies firm positioning and willingness to call the party out since 2016 has given people a different image of what a progressive leader can be, one that doesn't jive with warrens image
On biden, he might mr magoo his way through to awin in the general. HRC was thoroughly disliked in 2016, i think biden makes up some ground there automatically. Getting the obamas on the campaign trail early will also help. Also, voter turn-out appears to have spiked in VA compared to the 2016 primary. If that trend continues across MI, WI, PA he can eke out a win in the general. Alot of what trump can throw at him goes both ways (corruption, gaffes, creep factor with women) so that may be blunted, although hypocrisy appears to be one of trumps super powers. The only thing i can see trump getting dinging him on is things like voting for NAFTA, and that he'd never won elections until this year.