It doesn't make sense that there will be no Dark Avatar expansioin pack - unless they combine it with Twilight of the Arnor.
As I said, DA is available as part of GC2 Gold, which was released to retail last year when DA came out. Twilight however is not currently planned to go to retail in any form.
I think its lame, but I'm sure their marketing and sales geniuses are going to squeeze every bit of profit from it that they can at the consumers' expense.
I'd say taking the (rather considerable) amounts of budget that would go towards marketing, manufacturing, etc, for a retail release and putting them into the game itself--resulting directly in more and better features--is hardly such as you describe.