Steve Paine at Time for the Carrypad blog has published a wonderful analysis of power consumption in Origamis.
Better screen panel technology is the key at the moment. They are inefficient and we will have to wait until new panel technology filters though into the correct price range. Battery technology is obviously important and again, the new technologies need to filter into common use before they are affordable. Miniaturization of components will help to reduce case sizes having the advantage that a 5” or 6” screen wont make it look like a toy. Processor technology needs improving and complete integration of CPU and co-processors is needed. Its going to be a game of cutting down here and there and waiting for better pricing on new technoligies.