I am curious about the same thing; what game this year will make me want to buy a new video card for Christmas? I haven't had trouble playing anything with my 5 year old HD6850; I usually play on high video settings too. The Xbone hardware isn't much better so ports should still play fine as well. However some modded games (Fallout Vegas) give me a hard time when it comes to large texture packs.
I figure that once large texture mods come out for Fallout 4 I will need to upgrade, but until then I think I am still good.
I thought Fallout 4 was supposed to be a 30 GB install size. If that isn't already using large textures, I'm not sure what all that space is going towards.