If you are looking for an answer to this question then you wont find an answer to that here. Probably no one really knows a complete answer to this question right now. A simple answer would be to have a mix of the Macro cells, Micro cells and Femtocells with some way to offload some more traffic via WiFi.

Earlier this month Skype announced that its client would be able to work on most Symbian phones. I have used the Skype client on phones from '3' and they work great. Skype is even available on iPhones and they were downloaded 1 million times in the first couple of days. Now a big chunk of operator profits come from long distance calls and calls when abroad. If we all start using our phones with Skype, its going to bite into the operators profits. That means they will have to recover this profit from us by another way.

Skype on phones will be used in always on mode, meaning that the networks will get loaded and get congested. A simple solution is to have Femtocells at home that can offload the traffic on Internet. These background apps do cause a considerable amount of traffic and recently an Operator blamed the apps for its network woes.

Femtocells have been targeted generally at the residential market with developments going on for Business users as well. Another smaller Picocells and Microcells are also easily and cheaply available nowadays. With the Ad-Hoc deployment of all these smaller cells, Self Organising Networks (SON) may have a big role to play.

What happens where there are multiple networks present in the same place via these smaller cells? Can the back-haul not get congested because of these multiple networks which may be lying Idle most of the time? How would these impact other services that we use on our PC's?

These questions can be easily answered if a single Microcell/Picocell/Femtocell was able to work for Multiple Networks. Practically this may not be possible right now because each network has a different Authentication and Security arrangement.