I think it will play out similar to this...
He will be asked to step aside. He will be offered to do so gracefully for health reasons. This will be done after the next debate where he will not have a teleprompter or cue cards.
If he does not step down, he will be taken out. This will be done at the convention.
In order to avoid concerns of racism and misogyny, Kamala will announce that she is seeking to run for Governor of California. This will allow a graceful entrance of Newsom to be the Dem nominee.
The Dems were hoping Biden would be able to hang in there and beat Trump, but it's now obvious they are going to lose, and the Deep State will do just about anything to keep its puppets.
The real question is if Biden will be able to hang in for eight long months and finish his presidency.