Telephone Poles: Soon To Be Only Found In Museums?

My wife got a new cell phone plan the other day, and had an off the wall thought. How long will it be until land line phones companies are pretty much non existent? For about half the cost of a home phone, she can answer calls no matter where in the country she is, make calls to anywhere in the country without incurring any long distance charges, enjoy all the same features that land line service offers, and can call people at night and on weekends without putting a single dent in the plan's minute package. Many people I know don't even want the hassle of another phone to manage. And since the popularization of internet VoIP (Voice over Internet Protocol), others have switched their entire phone system over to programs that incorporate their broadband or DSL connection into functioning, reliable, and inexpensive telecommunication devices. So anyone care to take a guess as to when land lines become completely washed up, because I really don't think it's too far into the future.