I think the trojan horse for voxel engines is lighting systems. There are already game engines that voxelizes the world to a very rough voxel representation to

I think the trojan horse for voxel engines is lighting systems. There are already game engines that voxelizes the world to a very rough voxel representation to efficiently calculate indirect light propagation. I think more and more lighting and physics simulations will be implemented in a rough voxel representation of the game world. Then, to improve accuracy and detail this representation will become finer and finer, until it makes more sense to render this voxel representation directly, rather than rendering the polygons. What's missing is perhaps hardware support for rasterization of polygons to voxels. It's hard to compete against the super efficient hardware rasterization of polygons to pixels otherwise. I think character models will be polygon based for a long time still, since it's much more suited for character animation.