At this point their hiding biden in the basement.
It's lose-lose for Biden here, really.
If he chooses to debate, he will get stomped because he will probably forget he's at a debate. If he hides in the basement, it shows off that he's weak and scared to face Trump. Someone who the Dems have been painting as soon dumb, and so inarticulate (he is really fucking inarticulate.) ...the message that sends might be as bad as going and losing.
I think he will debate. Not debating is a surefire way to look weak. In a debate, maybe he might be able to keep it together just enough to be more articulate than Trump, and come out not looking as weak as if he had skipped it. Or even win sympathy points if Trump is too mean to the fragile old man.