Because of the amount of time that it takes to produce full total conversions on the more modern engines, our team has started to produce media and game play concepts before the id Tech 5 engine is released.
The Tech 5 (RAGE) engine is going to be fairly similar to the Tech 4 (Doom 3), so we already have a good idea of it's programming limits and engine structure. Because of this, we are planning out all possible details of the game that can be planned out at this point, as well as building hi-res models of all the characters and enemies. We will be able export these models into whatever format is needed once we get the engine.
Game play concepts, which we test through rough paper/digital prototypes, will be refined to a state that they can be implemented with relative ease once the engine is in our hands. Because of the prototyping, theoretically all of the design bugs will be ironed out before the actual programming begins.