It seems it isn't really easy for them to release it - I mean at least it seems that way when you read Marks twitter messages.
I have no idea whats behind this with license and all but if possible it would be great if they release all songs in the game. They don't have to press a CD, just releasing it as digital download would be helpful.
But I guess they would do it they could - it seems an easy way to make money and for DA4 they will likely have new music composed. So I guess there are some difficulties we don't know about.
But Bioware please: release what you can, especially the dread wolf track.