No. Only a small subset of cell phone users will be able to use that app. First you need a smartphone, which usually has an expensive data package. A lot of people are happy with their “dumbphone” and don’t want to pay for a data plan. Second, the smartphone has to be running Android 2.0 OS. Android phones simply haven’t taken off and even with the new phones and new OS, I don’t think Android will be widespread. Even if the app is ported to the iPhone OS, there will still be a lot of people out there who won’t have a phone that can run the Google navigation app. I don’t think people will change phones and plans just to use the Google app. They’ll just keep using their old phone and buy a regular GPS navigation device.
Then there are the issues of battery life and processing power of the phone, screen size, user interface, handling navigation and phone calls at the same time, and having a data signal when in rural areas.
Yes, many people will adopt the Google navigation app, but there are many reasons people will stick with the traditional GPS device.