why are you wasting so much energy on all these words?You're working on a few assumptions. You're assuming Biden won't run for a second term. You're also assuming that if Biden isn't fit to run for a second term that he'll finish his first. You're also assuming that Biden's vice president wouldn't be the presumptive nominee if Biden didn't run for a second term.
All of that would have to be true to get a progressive candidate in 2024 instead of 2028 or 2032 if Biden wins. I'm not rooting for Trump and I'm not banking on some future progressive candidate that doesn't currently exist. If there was such a candidate in the future, why should I believe that the party establishment and the mainstream media would treat them any better than they did Bernie?