Well when they brought up the issue on the BioWare forums after the specs were announced and people were worried about the low file size, the developers came in and said that it all had to do with a new compression method for the audio files and the textures and shyte like that and that the lower file size wasn't because it had significantly less content than DA:O but simply because they had gotten "better at making games."
This was the exact reply:
Oh for the sake of bacon. It is this sort of doom and gloom naysaying that depresses the heck out of me. "Oh, I don't really understand how things work in the industry, but 7GB is less than previous, so it must be bad."
I shall try to explain in 3 main points why Dragon Age II is 7 GB.
1 - We used a different compression scheme in DA II than DAO (something called "ogg" I am told).
2 - 2 less fully VOed langauages
3 - Optimized mesh data, physics and lighting (which I am told reduces the footprint of environments by close to 75%)
I know some will still doom and gloom, but the game is 7GB because we are better at making games. So, now that you have some reasons why the game is 7GB I hope this will calm some of you down.
Now it's already been mentioned that DA2 will be a bit shorter than DA:O and it seems obvious that they've cut out some corners with the options, but I don't think it'll be that bad. In the same thread it's mentioned that games like the Witcher and the Witcher 2 both only needed around 8GB's of space.