FWIW I think 10gb *is* enough. I think the 3080 is a decent card, minus all of the shenanigans. And the bait and switch pricing and etc.
Nothing will convince me 8gb is enough though. It may cling to life at 1440p for a while, but never what I could even consider close to the lifetime of the card.
I had my Titan XP I bought used for 3.5 years and if I still had it it would still be a fantastic card, more than good enough for 1440p. I suppose if you are happy replacing it (3070) in a year or two? fair enough. It's your money after all. GPUs these days seem to last a lot longer than ten years ago that's for sure. I used to upgrade every year or two then, as I hated playing new games looking like 'doo. Now? I am happy to just leave it be, until it becomes an issue. Which oddly enough in the 3.5 years I had it my Titan XP never was. I mean yeah, it went from being a 4k card to a 1440p card. So I bought a 1440p monitor (cost me way less than a new GPU). TBH I am happy with 1440p any way for the most part, but do render some games at 4k using DSR as I feel it improves them.
I mean look this is the same old crap going on when Nvidia released the 6gb 1060 and the 3gb. "Buy the 3gb ! it's not worth the extra, it's more than capable blah blah". Only if you bought the 3gb? congratulations, you now have a paper weight. The same reason why the 780 and 780Ti are now pretty much useless, even if you were hanging on at 1080p and why the 970 is still enough (because it has .5gb more lmao).