We're missing models, maps, the engine, and possibly animated scenes, though I doubt it.
That could be 2 more preloads at one a week, plus a final one to unlock it, if it went gold after 2 weeks it COULD make a sept 30 release date, though I wouldn't put my faith in it.
Because wav file are enourmous. I think wave files are 10x larger on average, at least that's what I recall. Morever, the audio loss in high bitrate mp3s is undetectable by most people.
And 16 hours of dialog is easily do-able. If anyone could get the numbers for doom 3 it would be a good...