If it really looks like that, no wonder it isn't done yet. How many game engines have they gone through now? Haven't they learned from Daikatana?
Look here, Wiki--It was originally on the Quake 2 engine
--Then, they jumped to the Unreal Engine
--In 2002, it was reported they basically scrapped 95% of the entire game, actually and were on the Unreal Engine 2.0, which they were heavily modifying engine.
--Then, eventually rumors floating they moved to the Doom 3 engine; who knows if they did....nothing was ever confirmed or denied...
--3D Realms also picked up Meqon for doing the Physics, dropping the Karma physics (which is in Unreal Engine) that they were using.
So, pretty much, gone through at least 3 or 4 Engines.....