You mentioned that 21Mbit/s isn't available on mobile networks today. Telstra has this working today and is imminently about to launch commercially, but could be beaten to market by 3 in Sweden if they're not careful.

Femtocells will still require a (wired DSL or cable) broadband internet connection back to the operator's network, so you won't be able to completely get rid of your wireline.

David Chambers
ThinkFemtocell.com