Thanks for clarifying Motorsep.
Interestingly enough I have found that 1536x1536 textures look slightly better than 2048x2048 in terms of jagged edges.
1536x1536x6 can still be compressed no problem.
As for rendering in 4K and down-scaling, there must be a more efficient way of doing this. Rendering a 6xstrip in 24576x4096 just to emulate anti-aliasing seems like a serious overkill to me.
I am using 3DS Max and getting anti-aliased cubemaps doesn’t pose a problem.
I believe this is also somehow related to how what is displayed is re-scaled for different devices. An app using the exact same cubemaps looks relatively ok on a Gear VR headset but the aliasing is much more visible when the same app is compiled and used with Google Cardboard.