Touchscreen provides convenience in maneuvering apps and browsing the web. However, it causes problem if the handset is hold towards the ear. Phone call could be put on hold by ear. Apps can be fired by face. With this consideration, 97% is probably is high number.
On the other hands, there might still be market of smartphones with small form factor. Touchscreen will be difficult to accomplish in a small phone.
Capacitive touch is nice in that it allows your fingers to act like a stylus however, I can't tell you how many times I've had programs open due to a slight brush of the screen. Very annoying. At times I wish that a hybrid resistive/capacitive touch screen was available to give the best of both worlds ... or a least the option of being able to change the minimum touch time before a program will open.
I can easily see 97% of future products with a touch interface. Have you recently tried to buy just a cell phone? You can't. They are all bundled with extras like cameras and touch screens. The era of single use devices has disappeared and since a touch screen helps facilitates mutiple programs, it looks like it's here to stay
Unless the touch screens work as good as the i-gadgets like iphone and ipad they are quite useless and clunky and simply raise the cost of the device and make users freakout. I know of many high end smart phones which still have a so-so quality touch screen.
I do see that cell phones are more or less replacing need of computer for email and social networking part, so touch screen is becoming requirement. Key is to figure out how can we make them more power efficient since they are most power hog other than RF part.