The Dems do not have a deep bench - the old politicians protect their positions and now we all are paying for it. That said, the next presidential election - IF THERE IS ONE - is more than three years away, and in politics that's a lifetime.
imo, the felon in the Oval will refuse to leave when this term ends; it would not surprise me to learn his team is working on just that now....and THAT is what the Dems should prepare the nation for now.