if he does resign because the next in line will be the same, but I believe that if Obama tells his allies that Joe is done, then Joe is done. Obama's CIA director and Ambassador to Afghanistan have already sounded off, in addition to the Senate Foreign Affairs head. There are cracks in the wall already. If momentum builds against him from his own party then he's in trouble.
Think of it this way: we always say that the Democrats usually vote en masse while Republicans have open disputes. If some Democrats break from Biden then that is a significant development.