There is zero percent chance Biden will resign just to give Kamala a win. If I were Joe though.. I wouldn't be eating any unsealed pudding cups if I were him.
There is also a zero percent chance that Sotomayor will retire because if she does, there isn't enough time to push through a new nominee for her spot, even though the Dems have control of the Senate. It would have had to happen months ago.. with the holidays... there's only like 20-25 days left where the Senate is in session until the new year which will bring about a Republican controlled Senate. They could easily filibuster that to prevent such a miscarriage of justice in putting Harris in the SCOTUS.