I'm guessing they've decided that they're going to replace Biden at the convention so they may as well burn the old man good while they can.

I don't think they will. The biggest reason is because it would be hard to get a new candidate on the ballots. Beyond that, it isn't hard for them to arrange for Biden to be elected. Either the elections are fake and they can make sure Biden is elected, or they are real and getting another candidate on the ballot isn't feasible. Then all he has to do is hand over power to Kamala or really anyone.