Ok. Time for a quick lesson on how US Presidential elections are dumb. Right now, Donald J Trump is the Republican Candidate for President. The ballots are printed, his name is on there come hell or high water.
Real big but here. You are not voting for Biden or Il Douche. Instead, you are voting for a slate of electors selected by each party. In each state, the candidate that gets the largest plurality of the vote gets to send their party’s slate of electors to vote in the Electoral College. The electors actually vote for the president.
They can vote for literally anyone. Their ballots are blank slips of paper. They put one name down for President and one for Vice President. They vote in rounds until a candidate for each office gets a majority of the electors’ votes. This happens in December. (If they can’t reach a decision, the House and Senate each pick a President and Vice President.)
So. If Trump dies, resigns or otherwise leaves office between now and December, the Republican party will make a loud suggestion of who they want their electors to vote for. The electors are generally all party loyalists, so you can expect they’ll vote as a block for the RNC’s preferred candidate. This does NOT have to be Pence. They could vote for Kanye and leave Pence in the VP slot or replace him with Sarah Palin. Anything is fair game. So, there might be some jockeying if Trump dies, but almost certainly not before. We likely won’t see most of it, as it’s going to be a backroom deal (within the limits of what the electors will go for).
Trump’s illness does not leave any room for swapping candidates or delaying the election [that wasn’t already there]. Also, if Biden gets a majority of electors, then it doesn’t matter what happens to Trump, there’s a clear line of succession to cover all possibilities there.
(And, why, yes, I think we should abolish the electoral college. It failed at the one thing it was supposed to do: allow electors to override the RNC and prevent someone like Trump from taking office. We can come up with other reasonable rules for what happens when a candidate dies during election season.)