It's the most likely outcome at this point, barring another major gaffe before next week.
It's either stick with Joe, or hand the reins to Kamala. Otherwise they lose their entire war chest of over $100 million banked. They also have to completely redo their campaign strategy to fit a non-Kamala candidate, whereas if it is Kamala they don't have to change much.
The problem with Kamala? She's more unpopular than Joe.