I don't know if we'll see a Game Boy Evolution (we need to think of a different name. Evolution was a play on Revolution. And Game Boy Wii just sounds ugly. XD). The DS started off as a third pillar. But that pillar seems to have taken over the other two. This year's E3 had a focus on the Wii and DS. GBA wasn't shown off as much as I thought it would be. And the GCN was almost nonexistent. The Wii, game play wise, is very similar to the DS. They share similar features and such too. I think just as Nintendo has gone this new way with their first pillar, I think their third pillar has taken over the second pillar and had some influence on the first pillar. Wow. That's a lot to wrap your head around. XD
Anyway...DS2 (which I hope isn't the name because it sounds like PS2). The current DS is in-between the N64 and the GCN. So, I think the next-generation DS will be between the GCN and the Wii.
Still two screens. Still a touch a screen. However, the screens will be larger. The control pad will be ditched for the thumb-strap and stylus. The buttons will be replaced with the same kind of buttons featured on the Wii (A, a, B, b, etc). This, of course, would make for an awkward interface. The majority of the bottom half of the DS will be a giant touch screen. Two configurations: Right handed and Left handed. This will determine the placement of the buttons in relation to where you will be playing with the thumb-strap or stylus. There will also be enough room that the user can still see an "area of play". If I've worded this poorly. Just think of it like this. The current bottom half of the DS. Only the whole thing is a touch screen. Control it on one side using the thumb-strap or stylus, touchable buttons on the other (it'll come with two thumb-straps), and in the middle is a spot reserved that would act like the current DS touch screen.
Tilt (not motion) sensors will be built into the system.
The Nintendo WFC will also be built into the system, not built into the games. It will also come with Opera built-in, as well as AIM or more advanced version of Pictochat.