If the bottom drops out over the winter (and I think at this point there is more of a 1/3 possibility that it happens, more than 50% if we get another COVID freak out), I think the Ds could very well be slaughtered in 2022...they also have until no later than January to pull the Senate and gubernatorial races out....maybe March for the House...afterwards everything gets baked in (due to retirements, money, etc). The Virginia governors race will be illustrative for how much the anti-Trump California playbook can limit the damage (I also think if the Rs lose this Virginia is going to tear itself apart....it's unsustainable state with confederate flags waiving proudly in the southern part of the state and Arlington being San Francisco blue).
2024 is a long way away. At the rate of deterioration Biden is going through, I think there's a reasonable chance he doesn't even make it to 2022. But if he is no longer president, it does give the Ds a chance to reset. Now they'll have to reset with Kamala (who hasn't even managed to do a good job as Veep in selling herself and makes Selina Meyers look like a political savant, at least so far), but we won't really know until we know and she will have a honeymoon period being the first female president and an African American one to boot. Who knows, even if she is an awful campaigner she might prove to be good at governance (yeah, I made myself laugh at that but again we don't know what we don't know).
It is a tall order and I stand by the statement that Trump might have done himself a favor by losing. If nothing changes, we are headed for a wipe out so large it might send the Ds back into the wilderness for decades.