Actually, I think it will be Warren. Although Susan Rice would be my choice.
Problem for Dems if Warren gets added to the Biden ticket is that the Republican governor of Massachusetts gets to choose who replaces her Senate seat. The chances of Charlie Baker choosing another Democrat are slim to none, and slim left the building awhile ago.
Biden’s campaign has a major Gordian knot of which female VP candidate to choose. Kamala Harris gives you zero (and quite possibly, negative) bounce in the crucial swing/purple states. Her record as District Attorney of San Francisco and Attorney General of California isn’t appreciably better than Klobuchar’s checked history as a County Attorney in MN. Klobuchar otherwise would be a shoo-in IMO, as she provides Midwestern resonance/balance to the ticket.
I personally think Biden goes with a minority for his pick. That puts Val Demings, Keisha Lance Bottoms and Susan Rice also into the mix amongst African-Americans (Stacey Abrams isn’t well known enough IMO), with Catherine Cortez Masto and Michelle Lujan Grisham the top contenders amongst Latinas. If there are no major skeletons in her closet, I’ll speculate that Grisham would be the choice. The title of governor will almost always have the most gravitas amongst politicians at the non-federal level (Sarah Palin notwithstanding).