I'm one of those that does not believe that Biden will be replaced. The DNC probably has decided to sacrifice winning the WH in 2020 and concentrate on the House and Senate.
Biden winning deals with the Sanders problem. That's their short term goal
I think they have shifted their game to using entrenched bureaucrats and Obama era judges to systematically undo or otherwise much up what good has been done. They got three years of 'impeachment' nonsense, deflecting investigations and prosecution from many high ranking crooks from the previous administration, and generally destroying the reputations of agencies and people. Unfortunately, the GOP hasn't exactly been the standard bearer for getting rid of such, (FISA, for example), maybe because they fantasize about using such against the Dems (unlikely to happen because they have so miserably failed to prosecute any but a couple of child rapist types, one of whom 'fell silent' before any trial.
Likely, a host of others have quietly met their demise either through moments of extraordinary and sudden despair, or unfortunate accidents and more plebeian criminal events like 'botched robberies'.
If they can keep a majority in one house, that will also enable them to hold critical functions for ransom, that ransom being funding for their socialist and pork barrel projects.
If they can provide pork barrel grants to groups which, in turn, sue Federal Agencies over policy or decisions, they can make enough of a mess of things to slow recovery, intensify real misery out there, and even crash regional economies, not to mention keeping policy from being implemented almost indefinitely.
