It just needs a few things:
OLED: Have you seen the size of the screen/tablet part? It's really thick. This thing has some serious potentional to be unstable when sitting on the keyboard/dock. The OLED would also extend that huge display's battery lifetime significantly, while decreasing the thickness.

OMAP 4: Multiple processors, better power management/ consumption, especially when using optimized software (which should become more common when these things really take off). Even without optimized software, they should be far better than x86. Also, the processers themselves will be faster while using less energy.

Optimized software: Mer is a good start.

Wimax, 3G, 4G, etc: One of these might drain the battery a bit more, but think about how much more useful it might be, especially if it had good management of those internet connection device power consumption.

Time: These things probably won't all fall into place for another couple years. The OLED is possible, but the technology is still crazy expensive for a screen this size and suffers from problems with the blue pixels. OMAP 4 is still a ways off. Mer should be the first to be ready, but even it isn't optimized for multiple processor ARM.