Looks like 8GB VRAM card not going to last long on mainstream 1440p.
Haha, what makes you think that? 3070 beats 6700XT in 4K and 3060 Ti is just behind 6700XT, like it's supposed to be
You can't use the Memory usage on a 3090 with 24 GB VRAM for anything. It's pointless actually. Higher amount of VRAM will always result in higher allocation and usage. Put a 3080 in, run the same game, same settings and VRAM usage will be lower, I will guarantee this. Same is true for system memory. More memory, higher allocation.
8GB is plenty for 1440p and this won't change anytime soon. 4-6GB is what most newer AAA games on high/ultra settings
actually needs at this resolution.
Looking at VRAM usage is useless, especially when some game engines just allocate all VRAM. You need to look for fps dips to see if VRAM is a problem or not. Not enough VRAM; fps drop to 0-1 fps for a split second. You will know something is up. It won't be smooth.
In 4 years, 8GB might not be enough for 1440p maxed out in true next gen titles, but you know what? Current GPU's will be too slow anyway. A high amount of VRAM is not going to save a weak GPU. So you will need to LOWER SETTINGS anyway, and when you lower these, VRAM requirement drops too. So, yeah...
Even the best GPU today will be beaten by mid-end in 4 years. Upgrading more often is better than trying to futureproof.