With screen resolution 1536x2048 (Landscape Left orientation) on iPad4 static variable "TouchScreenKeyboard.area" returns keyboard's portions as it would be for 768x1024 screen resolution. Take a look at the screenshot "iPad4-1.PNG". Area coordinates should be something like this (x: 0.00; y: 834.00; width: 2048.00; height: 702.00).
Also, the same issue happens in portrait orientation. Look at the picture "Pad4-2.PNG".

!!! Also, this might be a bug, that input text line's height is not added to keyboard's height. But since input line can be hidden,this might be not a bug.