I can say with conviction at this point that the next generation games are still going to be predominantly polygon games. Even what we're looking at for id Tech 6 with all of this infinite geometry, voxelising everything, probably recursive automatic geometry generation - all of this is still going to be a hybrid approach. We hope that we can generate these incredible lush environments on there, but the characters are probably still going to be coming in as triangles over a skeleton there. There will probably be some interesting things tried with completely non-polygonal renderers, but the practical approach with games that look like the games we're doing now, but play better, probably will still have lots of polygons going on and these chips better be really good at that.
Full voxel based games with many dynamic objects and characters are still too demanding for next generation technology. On the other hand, a scene with few dynamic objects (such as the Ruby demo) should be entirely possible with voxels only.