Great. But exactly none of that benefit is lost if you also increase resolution.
In fact, by increasing resolution, with respect to your point about being able to keep things the same size and gain more screen room, it means that, in the case of bitmapped graphics such as icons and sprites, there is no work for the developer. If you leave resolution alone as you suggest, now you need to redo all those images at a lower resolution in order to achieve the space gain.
Let me ask you again: you said earlier that you expect both screen size and resolution to change in the future. Can you describe specifically what you are envisioning?
For a two hour movie holding the phone is already uncomfortable.
Speaking of movies, if we make the screen 16x9 then the movie will display larger than it would have at some other aspect ratio of the same diagonal screen size. Or we can make the diagonal smaller than it would need to be at such a non-16x9 aspect ratio, and still get the same size movie.