For anyone else subbed to this thread, waiting for Voxel terrain, we now have a few options:
GitHub - Phyronnaz/VoxelPlugin: Voxel Plugin for Unreal Engine - Open source plugin, but it stutters on LOD change (at time of writing)
https://www.unrealengine.com/marketplace/voxel-plugin - closed plugin, but it does no LOD
GitHub - bw2012/UnrealSandboxTerrain: [WIP] Unreal Engine 4: Smooth voxel terrain plugin - been around for a while, still getting updates
http://runedegroot.com/open-source-voxel-terrain-editor-for-unreal-engine-4/ - just saw this while googling to find one of the above plugins