Eheh. That keyboard looks 100% like the one in E71. So I'd first look at which model of E-series this might apply to. Also, just because of schematics, doesn't mean the implementation(s) look like the schematics. For the patent doesn't include the keyboard as being part of the patent it is merely used here in the example. Perhaps for good reason, perhaps not.
That is: Leave the form factor the same as the N810 however, when the tablet is held upright as in fig. 4, the active application auto-rotates and reduces to take up the top half of the screen. An on screen keyboard appears on the bottom half (if selected as a user preference ). Rotate the beast back to landscape mode, as in fig. 6, and the app re-sizes to take up the full screen. If the screen is tapped in a text field and the keyboard is closed, an on screen key board pops up a la the N800. When the keyboard is open, it behaves as the N810 does now.