Wrong wrong wrong. AMD out 8 gigs of vram in their cards because they performed better even when their was vram to spare. I had a 290x (trix) and if it only had 4 gigs of vram then there is zero chance I would have been able to run witcher 3 at 4k30 or 1440p60 on that card. Same goes for doom 2016, 4k in vulkan on max settings I could get over 100fps but if I had 4 gigs of vram? Nope.You shouldn't worry.
In order to use more VRAM in a single frame, you also need more bandwidth and computational performance as well, which means by the time you need this, this card will be too slow anyway. Resources needs to be balanced, and there is no reason to think you will "future proof" the card by having loads of extra VRAM. It has not panned out well in the past, and it will not in the future, unless games starts to use the VRAM in a completely different manner all of a sudden.
There are however reasons to buy extra VRAM, like various (semi-)professional uses. But for gaming it's a waste of money. Anyone who is into high-end gaming will be looking at a new card in 3-4 years anyway.
So the card was not past it's usefulness by the time the memory was needed. I have more examples but point made.
Also PC gamers that are REALLY into high end gaming tend to upgrade their gpu every year unless the performance uplift is only like 15%. I have a 2080ti and will likely upgrade to a 3090 although I'll wait for game benchmarks to see how the 3080 performs.