I think it will be mixed, using both pointing device or touch screen, and voice. Some things are easier with a pointing device. For example, when browsing the web, I could rather touch or click on a link than saying it out loud. But other things are too complicated for a UI. Like saying "please use the photo I took of that dolphin last weekend as background" is much easier than finding the option to change the background, finding the dolphin photo and then selecting it.