There should be no need to have up to three different telephone systems in the home.
(1) Home wireless network of cordless phones.
(2) VOIP with cordless phones.
(3) Mobile phones.
There appears to be no technological reason why the mobile phone could not be used for all communication.
If the mobile phone could be used for all voice communication and shared with the broadband computer for data and video, this could provide both a cheaper and simpler integrated communication system.