From 3DGE Wiki
The features listed as In-Progress are features tied into the engine currently, which need to be finished up.
- PolyObjects (available in the latest devbuilds, more types will be supported in the future)
- Normal/Spec/Brightmap support on textures
- Rise of the Triad support (ROTT_*)
- Dynamic Planar Shadow System for Dynamic Lights (Models only)
- Quake 3: Arena-style shader-based sky system
- Better BOOM Compatibility
- Decals on all surfaces
- TERRAIN.DDF: new DDF type for floors, that can do all sorts of neat things according to what flat name is being accessed at the current time.
- SPRITES.DDF: new DDF type for plain sprites, to control things like Offsets, Brightmaps, etc.
- New Input system, for split-screen controls
- Wolfenstein 3D support (WLF_*)
Future features are features that are not yet tied into the engine, but support will be coming soon for them.
- DECALS.DDF: new DDF type for wall decals (bullet holes) and floor decals (splats, explosions, etc)
- IWAD Selection Dialogue Box (like ZDoom)
- Blake Stone support (BLK_*)
- Strife IWAD
- Completed Heretic support, including an Inventory system
- True Networking, for internet play