I agree, but I use that same argument against Trump in this next cycle. Polls have him way ahead in the GOP primary, but that's before you get 5 other GOPers calling him a treasonist and a threat to democracy for 6 months. That could roll off his back or it could cause the public to jump on someone else. There's just so much time and these campaigns are really long with a lot that can happen.
The treason angle doesn't play well in the GOP base because they don't believe it, that's almost 100% a Dem thing. You are right though, early polls don't mean a ton right now until people declare, but Trump is still the most popular politician in the GOP and the establishment guys like McConnell are the least. No one "of worth" will challenge him because they remember what happened in 2016, but you might have the professional election losers like Evan MacMullin or Joe Walsh do something. Maybe Liz and Kinzinger too but they will never run 3rd party because that would take away Biden's votes and hand Trump the election like Perot did to Bush in 92.
Unless Joe steps down for health reasons, over 50% chance it's Biden/Trump again. I would prefer age limits on these things but that will never happen.