Possible because that person and their camp of supporters don't want to come out ahead of Biden formally making his own exit. That would like cutting down an incumbent. That is still a sin in the DNC.
Of course, it should be clear that "making his own exit" is noe pretty much impossible as anyone paying attention sees that he is being heavily leaned upon by some unidentified significant influencer(s) of the Democratic Party with influence in the national media.
I have looked at those who are making the call for Biden's exit. And I have looked to find out what 'camp' it is that could be home to this effort. IMO it does involves a majority of people who come from a similar branch of the democratic party "tree", but, of course, it isn't only limited to that pedigree. One might say that the fox is hiding among the tall grass or one might say that there is some variety in the people have doubts about BIden. Certainly the members of the House who must be re-elected to stay relevant have fear about the top of the ticket not carrying them over the finish line as winners.
I have a favorite group of suspects, they are politicos, and former politicos now in the media or acting as advisor/consultants in the privately funded punditry. But as that group is based on nothing more informed but circumstantial conjecture, I'm not going to cause a storm on DU by giving names or naming a likely replacement.
I'm pretty sure that people who take the time to look can certainly find similarities as I did by tracking personal histories of the players as it appears on the internet.