While many here have only read what others are saying about 4K and most of them have not seen it either. I know Dfergie and I have seen 4K and 8K in 2D and 3D.
The best way I can describe it is this. 4K over 2K(what we all have now) is not so impressive as it just offers a subtle increase in detail, especially present in extremely wide shots like crowd scenes. These increased resolution images will be best displayed on large screens as opposed to small ones. Thus the Sony 84" for introduction.
But as dfergie said, combining 3D and 4K {with an FPR screen ( passive) } is what makes 4K really rock. The reason for this is with present 2K passive the resolution is actually halved in 3D. This often results in jaggie diagonal lines, especially noticed on the larger screens 55" and 65" Not so much on 42" and smaller.
It's nice to quote writers of these blogs and magazine articles, but all too often many of these guys haven't even seen what they are writing about.
In the LG demo of their 8K panel they showed side by side of current day Blu Ray video ( 2K) on the 8K display and there wasn't much improvement, but when they showed the possibilities of 8K source video displayed at 8K on the large screen is was indeed impressive. Therefore I would conclude that 4K panels at 65" for current Blu ray will not offer as much impact as the gain of 3D BD on 4K passive. And, LG did show this comparison side by side.
4k is pretty cool, but I still like 3D effects better and when they are joined it will rock.
