I can imagine the conspiracy theories that will emerge if this comes to pass and these comments are dug up.
Sadly the conspiracy theory that Biden would accept the nomination and somehow transfer it to Hillary or Harris (and less frequently mentioned Bernie / Obama) has made the rounds on the internet already a few times already. As you might expect the predictions have morphed a bit lately, like such conspiracy theories always change with no intellectual honesty that the dozens of other predictions were dead wrong, but the moment something happens that even seems like one of them, blamo someone will claim a sort of prediction victory.
If that does happen: for the record I'm stoked Biden won, and the comment was just a light hearted joke.
Would Harris become the president if Joe Biden died before he is sworn in? Or would the electoral college select someone different? I think the constitution is pretty clear on succession if the president dies, but what about the president-elect?
It's clear on that, too. Check the 12th and 20th amendments.