The Trump core will stay with him.
Independents tend to be an emotional group in that their voting is based on their situation at voting time - they are not attached to either party. If their money situation is bad at that time, they will not vote for Trump. If the virus has come back in a bad way, they will not vote for Trump. In other words, if something is badly wrong, they blame the man at the top no matter if that is a Democrat or a Republican.
Since we can't know the US situation near voting time in November, I have no sense of which party will win. By September, and for sure October, we should have an idea which Party the Independents will favor.