In countries such as Austria and Italy, mobile operators are heavily promoting the use of their HSDPA networks as an alternative to DSL access at home. Pushed by very interesting prices starting at €10.- a month for 250MB, €20.- for 3GB and €50 euros for 20GB in case of One in Austria, only the sky seems to be the limit.
I've recently been in Austria and talked to a number of people using these offers. Being mostly students, they like Internet access via 3G networks for two reasons: For many it's cheaper (!) than DSL at home and they usually use it with a PC card and a notebook not only at home but also in other places.
For families, however, the equation might look differently. In many cases, several PCs or notebooks are available in the household and thus Internet access needs to be available to all family members. It can be done wirelessly for example by using a 3G/Wifi Access point but it of course immediately takes mobility out of the equation. On top, if you have kids then any kind of usage cap is just waiting to be stepped over as soon they start using file sharing applications, music downloads, YouTube and other bandwidth intensive applications.
So in the long run I expect mobile households to use DSL or cable coupled with Wifi to share a flat rate fat pipe with all members of the household, 3G/4G data cards in their notebooks for Internet connection while on the move and mobile phones which make good use of high speed wireless networks (3G, 4G and Wifi while at home) for anything from podcast downloads to video sharing. Wifi at home also has another advantage over using the 3G/4G network: It's possible to communicate with your network enabled household appliances such as digital video recorder, music library, other PCs, mobile phones, etc. A good step towards the hyperconnectivity vision of Nortel's CTO John Roese.
In such a scenario I it's quite o.k. to have reasonable volume caps in place for 3G and 4G networks. This encourages the use of DSL/cable at home where I think most data traffic will occur due to the availability of big screens which require a much higher bandwidth for video applications than small screens on the mobile phone. Also, people have much more time available at home to communicate, to work and to play. After all, no matter how far 4G will push wireless capacity limits, DSL, cable and fiber will have infinitely more capacity available than wireless systems.
Network operators with both fixed line and wireless assets will surely figure out how to make interesting dual offers and can thus insure that the DSL/cable backhaul and not their wireless network deals with most of the data traffic. The high speed cellular network will then only be used as an overlay network by most people when leaving their Wifi cloud.
Surely there will also be people that use the 3G/4G wireless network as their sole access to the Internet. I expect, however, that their number is small compared to "converged" users which increases the chances that enough capacity is available to transfer their data traffic alongside the data traffic from people using it as an overlay network at a comfortable speed.
As always, comments are welcome!