If he feels it will help him to win the election he will. I suspect he'll take his cues from his base, whatever they seem to want. Much of it will depend upon just how ill he becomes. Turns for the worse in Covid patients are fast and furious, opposed to a languished recovery.
I hope that Pence won't bow out of the debate next Wednesday, but I think it more likely he will given this golden opportunity.
Ms Harris as a former prosecutor will have that magical thinking space cadet for breakfast, lunch and dinner in a debate, and the Republican hierarchy knows it.