I think he's speaking moar about policies.
He tends to refer to Bernie as representing the most extreme of the radical left talking points.
Biden has to adopt the extremist ideologies in order to appeal to the voter base.
Hence, Bernie replacing Biden, metaphorically speaking, of course.
But Joe could croak at any moment. Which is no surprise. So, perhaps [DS] still might try the swapperoo as a last minute head fake. But I think they are fucked either way, and we all know it, and we're just here delaying the inevitable, as always…