Well, beware of Euclideon : it's not their first attempt at raison money, they are here every few years, they get some money from investors and they disappear...
Like in 2010 :
(back then, they were called "unlimited details")
They also did it in 2007, but I couldn't find the video.
It's NOT 2D plains, it's some well written sparse voxel octrees... This is neither new nor specific to those guys,
does it very well too. Why isn't it used in video game yet? Well, Carmack once said he wanted to implement it in ID Tech 6, but since he moved to Occulus VR, we are probably never going to see any of this.
So, problems :
- no GPU accelerated rendering (well, you can argue you could use GPGPU, so let's say no specialized hardware).
- Real time lightning would be a problem, so back to fully static light.
- Animation, while doable, would be power hungry, inefficient and very costly; so we would have to fall back on polygon for anything non static.
Even with such a list of problem, one game tried a similar approach, the infamous Outcast... It needed such a powerfull CPU and couldn't use the GPU at all, and that backfired as you can expect : back then, a lot of PC gamer were just buying their first 3D accelerator and were frustrated to see a game running in such a low resolution.
So yeah, interesting technology. Let's wait 2018 to see it come back again ^^;