I'm predicting you'll get your wish sometime after 20JAN23. This preserves the VP rights to run for two full terms which could make Harris the first 10 year President since FDR.
One condition is that Biden ends on an up-note. The date is good for Harris and the Democratic Party but every President wants a legacy. Most Presidents want a positive one, but some, like the previous one, don't care as long as their name is at the top of the page.
Therefore, I think Biden will hang on until he can leave on a positive note such as the economy on an upswing and forecast to stay that way. Mostly that means the global economy being able to manage the COVID pandemic with minimum economic cost. This should happen by early 2023.
Who do you think would be a good VP? Klobuchar? Buttigieg? Gillibrand? A fat, ugly one to keep Harris lookin' good? LOL
I do not agree that its likely, but I agree its possible. Of those you listed, I think the smartest s Buttigieg, he also has the most charisma, something that is lacking in the current administration.