Fair point. I think they would absolutely go with Harris. Partly out of deference, partly because she would remain in control of the Biden/Harris $100 million warchest and ground operations org, partly because her name can’t be taken off the general ballot in multiple states, and partly because Democrats need to campaign on women’s rights and it would look awful to pass over a Black woman.
I also think that Newsom/Whitmer/Beshear/Pritzker et al are not interested in replacing Biden. They will inherit chaos, are very likely to lose in the general, and that will be the end of their presidential aspirations.