We've just merged some code to automatically scale up the on screen keyboard in landscape on larger screens like tablets also allowing it to use more horizontal space.
While at that we also added the necessary bits to scale up font and icons on the keyboard's keys accordingly which also helps on phones when going to higher resolutions.
There's still some low hanging improvements like scaling down in landscape on phones or improving the touch area for the shortcuts and completion bars. Let us know if you want to help with that!