Precisely why I don't expect either to kick the bucket anytime soon and definitely not before Xmas !
And yet, you keep insisting that Biden will not be the Democratic candidate come November. No matter what you read on the dark web, notice that it is Biden who runs unopposed. Nikki Haley is still running against Trump, and that has to be, in part, because there are a few different reasons to believe he may not be the Republican candidate by November. Chances are slim, but: a) his legal troubles could see him unfit; b) the 14th Amendment could yet be invoked to make him unfit, c) the RNC could decided he can't win, d) ill-health.
Neither of these guys has to die to take them out of the race due to health. A stroke, mental unfitness. Biden has no legal issues to deal with, right-wing extremist theories notwithstanding. His issues would be health, or lack of popularity. Basically, he would have to agree to step aside. I don't see a coup at the convention. I'm linking a Politico article that posits how Biden could be replaced by the Democratic Convention next summer. I don't agree with all of this guy's premises, but he's not wrong on the procedures and the roadblocks to it. Not the least of problems would be that it would take the selection out of the hands of voters and give it to the delegates. This would not be that easy to sell to the rank-and-file.
The political and procedural steps for how to pick a new presidential nominee.
www.politico.com
Notice that there are several potential alternatives listed in this article, and none of them is Michelle Obama.