I thought Warren was running for VP, but after such a poor showing on Super Tuesday, she has nothing to offer Bernie.
With Warren out of the way, Bernie’s power move is probably to announce the Wookie as his VP pick. It would cut the legs out of Biden’s Obama association and virtue signal ‘diversity’ (black, trans-woman VP) at the same time.
I think it will be Bernie / Elizabeth vs Biden / Michael
I don't think Ma Obama would be interested. Obamas would rather save their card to play later. But if she ran as VP for Bernie or Biden and they won the election (unlikely), odds are either old man would not be in office for a full term.