In 20 years there will probably be keyboard instruments that do things we can't even imagine today. That might include playing or reproducing any style of music to that point in time, provide full synth and workstation capability as well as offering a user interface with voice command or some other to be determined way to interface. What we call Arranger will still be there only more powerful. We may see a keyboard that can be instantly configured to perform in many different ways as different types of memory become available and affordable. That will go hand in hand with new sampling technology that will allow even more accurate voices. Also maybe even keybeds themselves whose feel, touch and response can be selected. And all this will most likely be in a keyboard that is very light and easy to carry. Just my guess for the future.