Like with cable and the telephone, the saturation point appears to be 85-90%. So market saturation will probably be a marketplace 2x or 2.5x what it is now. Then, consumers will replace them either because they no longer are capable of doing what they need to do, break, or the consumer just wants the latest or greatest. Large number, but it is not even close to being a plateauing market.

http://www.pcmag.com/article2/0,2817,2420197,00.asp