So you don’t think Joe or Don will be the candidates. Why?
By then, Trump will be nearing the end of his second term as President, and will be Constitutionally ineligible to run for another term, per the Twenty-Second Amendment.
At this time, it is already quite clear that Biden's physical and mental health has deteriorated enough to cast serious doubt in his suitability to hold office. By 2024, if he's still even alive, I don't think there's much chance that anyone will be able to still sell him as a viable candidate for anything.