A question that bothers me about a potential future Descent 4 is whether it will be DirectX or OpenGL (or both). Imo the XBox is the most attractive game console out there for a game like Descent 4. The PS3 is too expensive and has too low a market share (or am I wrong?). Using DirectX would get you both the XBox and PC market. Afaik you need OpenGL for the PS3, which might mean you'd need to cut back somewhat on graphical features (the question is though how many of them you can do with OpenGL 3, and how important these features are, and how many people will have hardware that can exploit them - I'd say a pretty lot by the time D4 might be a reality). Third option would be to support both OpenGL (3) and DX (9,10,11 (?)), but that would be extra effort and would require some really good project management and code structure to keep the complexity as low and the high level API as consistent as possible. If it was up to me and the time and the money would be there, I'd opt for both render paths, as they'd also give you Linux (the market share of which is totally negligable though, and looking at the development Linux takes, this probably won't change any time soon), and OS X (another 10+ percent of potential customers ... why not?).
Another interesting (and imo preferrable) option would be the use of a good third party game engine and concentrating on the game instead, using the resources you save by not having to build (yet) a(nother) 3D engine to build a truly fabulous game with impressive environments, enthralling gameplay and a really good story on the level of Half-Life, Deus-Ex or Bioshock. If I'd have a say in that, the single player campaign should be 40+ hours for all people except those shooter experts that rush through each area w/o looking left or right in order to beat the latest speedrun record for the game.
I'd love to use an id Software engine for that. The question is whether it is affordable.
Descent 1 & 2 for Windows, OS X & LinuxOnly a dead troll is a good troll.