No doubt the future of web-based learning involves the use of multimedia such as audio and video. We can already observe on the web how much graphics adds to the experience. As is often said, a picture is worth a thousand words, and a moving picture is surely worth much more. Also, we can't begin to place a value on what audio adds to the web. As bandwidth increases, we will see an amazing transformation from text-based online lessons into true multimedia "classroom" experiences. E.g., imagine how much richer a virtual walk-through of a house is in comparison to a verbal description of its floor plan.
But here's a word of caution. We are all anxious to develop engaging multimedia lessons online, but this will take much time, money, and effort. Unfortunately multimedia content requires much more bandwidth, and technology, than is currently available to most. Until most people get better access to the Internet, we will need to be innovative, creative, and perhaps reserved. We will continue to need to use a lot of text, but we can find ways to innovate. E.g., in the meantime, we can put our larger files on compact disks or DVD's.