Since this question was posed, Newsom has seen his stock rise, possibly dramatically. JPK's stock also seems to be rising. I don't know if Inslee will ever be viable, but his recent leadership on the public health front would help his cause if he wants to try again. Bullock is also building a strong record and could easily get more DC attention as a senator in 2024.
Whitmer, the Squad, all of the Northeast Dem governors (nursing home screwups, etc), and the labor left in general have seen their fortunes decline. Yang could be viable if he gets elected mayor of NYC first and successfully cleans up the current nightmare there.
The problem is that another loss to Trump would be seen as an indictment of giving too much power to the social liberals at the expense of the traditional left. Then again, 2004 was seen the same way and it ended with a lurch only to the center of monetary issues and a lurch to the left on social ones.
Who knew in Febuary 2005 that we would have a black president, a constitutional guarantee of hay marriage, and be very close to a D majority on SCOTUS (that didnt happen but still)?
At that point, even some activists were about to concede that maybe should wait another 20 years on the LGBT thing and maybe we should try to compromise on abortion beyond what Roe would currently allow.