I will be quite satisfied if the GOP takes just one dem seat to end their majority. Cuz then Biden won't get to fill nearly as many judicial and executive branch positions as he would over his last 2 years. And even more satisfied if they can get several more than one. Picture this: it's 2024 and the GOP now has a Senate majority. One of the liberal justices on the Supreme Court either dies or resigns, Breyer most likely, he's a liberal, right? Biden or Harris, whoever, nominates a liberal/progressive to fill that position but the GOP doesn't confirm the guy. Heads would explode on the Left. Or, one of the conservative justices die or resigns, like Clarence Thomas maybe. The lib/dem president gleefully nominates a lib/dem to replace the conservative Thomas but the GOP controlled Senate doesn't confirm the guy. Same deal, exploding heads.
Anyway, I think there's a very good chance the GOP will also take back the House from the dems too. Happy days! A repub Congress and a dem president, which probably means not a lot gets done until 2025. BUT - if that happens, I think there's a fair chance that Biden resigns due to poor health (physical and mental), which would probably be true if it isn't already.