I'm unconvinced that this is likely until at least 2010, if not 2012 or beyond.
Experience with picocells suggests that enterprises are wary of having operators' equipment installed on their office LAN, especially if it has to tunnel its traffic out through a firewall. Operators are equally unhappy to have their base stations beyond their control on someone else's network. There may be regulatory issues here too. In theory, they could be installed on a virtual LAN using the building's spare cabling - but this still has the problem of manageability and ownership for the operator, as certain components like patch panels and fibre risers will be shared-use.
Instead, picos are often installed on completely physically separate cabling & infrastructure. Which is not inexpensive. Given that femtos cover fewer users / less range than picos, it seems to make the problem worse, not better. Distributed antenna systems may be easier, especially as they can be used for multiple operators' networks, while picos/femtos can only be used for one carrier, and are therefore useless for visitors, or where enterprises do not want to be locked into longterm deals with a specific single operator.
Also a bunch of other issues emerge:
- Channels - integrating femtos with PBX channels & system integrators will need years of recruitment, training & certification
- Value chain - lots of new "moving parts" will need to be brought into the ecosystem, such as RF design houses capable of dealing with cellular inbuilding coverage
- Software will be needed that can recognise a group of femtos as being part of the same "zone" - perhaps 30 on one site, 20 on another, and 2 in each of 100 branch office sites. Not that difficult, but to my knowledge nobody's done it yet
- Integration with IP-PBXs, and ways of dealing with legacy systems and migration. Another huge task.
And then of course there's the small fact that even simple, single-femto consumer deployments have yet to be developed fully, let alone rolled out.
Of course, dual-mode enterprise WiFi/cellular isn't that easy either. But it is "here and now" (albeit belatedly), and by the time all the issues above get fixed, it should be pretty mature. So in other words femto-based solutions will have to work well with that, as well.
The ultimate solution is some sort of mega-hybrid, embracing cellular, dual-mode, WiFi-only, DECT, IP centrex, outsourcing where appropriate, mobile PBX extensions, fixed hard phones, PC softphones, indoor cellular coverage with picos/femtos and DAS.... and having customers that understand it, enterprise applications that integrate nicely with all the devices, and channels that can sell the right solution. Now I think about it, maybe 5 years is optimistic.....