First of all, while I am no fan of Trump, he is in my prayers, and I hope he has a quick and full recovery.
If, heaven forbid, the worst happens and Trump passes away or is incapacitated, it will be a Pence vs. Biden election on November 3rd. Should something happen to Pence, Peloski (yes, Peloski) becomes president, which may have very interesting effects on Barrett’s Supreme Court nomination. In terms of the presidential election, should both Trump and Pence go, but Trump gets the majority of electors, the electors, probably in cooperation with the Republican party, decide who gets the White House (I wonder how electors in states which don’t allow faithless electors would handle the situation).
I think Pence has more of a chance to win than Trump does; Biden will have to give us more than “I’m not Trump”. Should Biden have gotten the virus at the debate. and succumbs to it, I don’t think Harris has good chances, although I think Trump vs. Harris is better for her than Pence vs. Harris.
If all die (not likely, especially with Harris), the electors will decide. It would be unprecedented, but Trump’s electors will probably choose some Republican, and Biden’s electors will choose one of the moderate democrats who dropped out this spring.