@Ryan: For the 3DS it will be a tough choice to lose the second screen. But it`s not like people would mind. Most people use always one screen on their phones, tablets, PCs, etc. It just that 2 is always better than one and the experience is less complex.
Don`t know if Wii U 2 will lose the gamepad. In a world dominated with tablets, it`s more appeaking than a simple controller. They might improve it.
Speaking of that, what if the next handheld and home console really are integrated into one?
What if the next home console comes in two SKUs? One with the controller and console and another just with the console.
The reason one comes just with the console is that the new handheld is actually the same as the controller (same but not in shape; in buttons, specs) that comes with the console. That way, people who already own a handheld don`t have to pay the extra 100 bucks (assuming the controller would cost that) and could still have both worlds: console games and handheld games, for less money.
So, even if the next handheld is less powerful, it wouldn`t make a difference.
This would also be important as it would provide a great value and faster penetration of new HW. Also, allowing people who would want another controller with screen to be already in possession of a new handheld.
Think it would work?