Graphical Enhancements:

Brand new graphics kernel engine. Better lighting, shadows, reflection, pixel+vertex shaders etc.
Progressive scene LOD (should help with performance during massive fleet battles).
Support for texture compression.
Decals support for falling snow, rain, blood and objects impacting water while on terrain.
Decals support for progressive damage on units (multi-texturing).
Volumetric fogging (for during snow and rain storms).
Particle dust for units moving on terrain.
Skeleton animations for character models.
Implement planetary terrain grass, vegetation etc (already supported in the engine).
Support for volumetric space weather areas (nebulae, space storms etc).