Is that a new timeline or one you’ve considered for some time?
The Democrats have a problem. Their nominee is going to go down in flames and bring in not only Trump but a MAGA Congress with a mandate for massive change. I'm thinking of something similar to the 1932 election. If they are going to protect their incumbents, they need a new nominee, and they need to get Biden out now, not later. The convention has to be a coronation, not a knock-down, drag-out brawl on national television. The party has to put its best foot forward.
I could see President Harris move Hillary into the VP slot, and the convention would reverse that, with a Hillary/Harris ticket, thus keeping a black woman on board, but out of sight as much as possible.