I'm pretty happy with the Paperwhite as it is. I rarely keep more than about 20 books on board and usually not that many. I find the light to be just fine. I have 2 Paperwhites and they're both evenly lit. I would like page turn buttons but it's a small thing. I'm okay with the way it works now.
What I would like to see is a more intelligent way of handling wireless. It should turn off when I'm not doing something that needs it and turn on when I am. Why ask me if I want to turn on wireless to access the bookstore or download from the cloud or sync? Of course I do. What a silly question!
When I'm finished with one of those things wireless should be smart enough to turn itself off. For those who have special offers (I don't) it could turn itself on periodically, update them and turn itself off.
As it is I like the Paperwhite so much that the next one is going to have to be very very good to make me want to upgrade. I've gotten every new model since the Kindle Keyboard, my first one, but the Paperwhite could be my last, or at least till the battery is gone.
Of course if the next one is a bit lighter and has a built-in inflatable recliner I might reconsider.
Barry