I don't believe in Post-Convention bounces much anymore, or at least in this election. Most of the people who are going to Vote Dem, hate Trump, will be voting for Biden. Plus in this case, it's not like there is a choice between choosing sides as Trump, aside from all that he has done, hasn't shown a plan for his 2nd term if he won it.
Instead all he has done is double down on his base, who would be voting for him.
So it effectively wipes out Independents as they will be voting for Biden for the most part.