I think that the 3 consecutive two termers we had recently (Clinton-Bush-Obama) was an aberration. Heck, we almost didn’t get Bush. Hard to say if Biden would be a one-termer. Trump is such a wildcard. He almost seems like he might be the easiest for Biden to beat. DeSantis could probably beat Biden if Trump didn’t run, but that’s me trying to predict something 32 months out.
I'm refraining from making 2024 predictions right now (which really hurts lol) because things are so volatile. Everything could make a complete 180° for Biden as COVID and its economic impact recede with vaccinations increasing globally, but there could also be a new variant that throws everything off. Maybe he gets a major win under his belt with his sabre-rattling, maybe he doesn't. Maybe we go to war somewhere. Maybe his health gives out, maybe Trump's health gives out, maybe both. Maybe one or both run anyway despite bad health and it effects their campaign. Maybe DeSantis primaries Trump, maybe he doesn't, maybe he runs with him. Maybe Trump ultimately doesn't run and backs DeSantis' opponent in the primaries. Maybe someone big primaries Biden or Harris. Maybe the Democrats play the idiot ball and randomly put Harris on the Supreme Court because they're so scared of running her, ironically screwing themselves for 2024 in the process. Hey, maybe there's a terrorist attack out of the blue that becomes the next big thing. We just don't know.
But with all that chaos, yeah, the two-term back-and-forth norm we're accustomed to isn't a guarantee.