In this highly computerized world I truly do not see the point of a person having a landline phone number. Anymore, everyone has a cellular phone that they carry around with them anywhere. Plus, if they want a phone line that they can have at home Skype is a great option as are many voice-over-IP or VOIP solutions could be a great replacement. Not only can you access you VoIP from anywhere over the Internet but, you can also save a lot of money, Skype out, or making a call from VOIP to a regular phone number is $2.99 a month for UNLIMITED calls to the US and Canada and for Unlimited calls worldwide that is only $9.99/year. Plus to get a phone number coming in to your computer for receiving calls is $60/year. That is only $96/year and you can take that number anywhere you go and if you want to call unlimited internationally, then it is still about $180/year. That is still probably a major savings over your regular phone bill and can go anywhere!
The one disadvantage, is that you cannot make emergency service calls but, cell phones are. Plus, you are now relying that your Internet service is not down when you need to make the crucial business call. Also if you have a cell phone, then you can take your phone with you anywhere.
I believe that, landlines will evolve into VOIP and will then make the move to primary use of cell phones and then when worldwide WiFi is developed cell phones will switch to VOIP-based cell phones. I believe that these evolutions have already begun and will take full-spring in the next 5 years and then the second revision will come about in another 3-5 years depending on the availability of an omnipotent WiFi network.