Seeing the new Apple Air made me think that the DS could undergo a similar transformation. First, geting rid of the GBA slot, that thing takes up a ton of space. Next, get LED backlighting. Technology has also improved since the DS Lite was released, so better battery life is possibly by using smaller components and better batteries.
Imagine a half in thick DS that folded up like a makeup case. The women would go nuts over it. Also, it would be cool if the case was metal.