A second Biden term would probably be rough for the Democrats in the long term. In the short term it'd be good because they'd finally eliminate Donald Trump from the political discourse and may be able to install a SCOTUS justice or two, but in the long term they would have to contend with whatever demagogue happens to pop up in his wake in 2028. I think Biden would be at Bush levels of unpopularity by the end of it. I also think progressives would eventually start steering the ship after he's gone - his brand of politics will become as unpopular as Bush is in today's GOP.
Trump's second term would be similarly disastrous. Democrats would be headed for a trifecta by the end of the decade while the GOP would never be able to ditch the Trumpists, being that they'd overtake the entire party. I legitimately think such a timeline would take us to a future in which Trump is the only Republican president in roughly 20-30 years.
you're silly.