The latest information I have is very much a split decision. Many of the smaller publisher I know, particular publishers of genre fiction, are fine with the query letter dicussing audience.

Larger publishers, on the other hand, don't really care for the writers' opinions on the audience. They have their own marketing departments who decide what the audience is going to be, and if the marketing people don't think that the book can be easily marketed, it really doesn't matter what the editor thinks (in many cases).