Looks like the much-rumoured WiFi/cellular BlackBerry is finally on its way. An outstanding question is whether the WiFi function will be accessible for carrier services (eg UMA, VCC), or end-user local connectivity (to a corporate WLAN or public hotspot) - or both.
I'll take a punt that the underlying platform will support both - although possibly not in all operator-specific variants.
I suspect that T-Mobile US may have come up with a superficially compelling reason for a UMA variant for use at hotspots (& maybe employees' homes), although it's not likely to be much use when the device is inside a corporate WLAN & firewall. UMA isn't designed to work with complex switched WiFi networks (Cisco, Aruba, Trapeze et al). There have been various noises to make some of these UMA-friendly, but they don't appear to have got anywhere substantive. One of the problems is that UMA needs to make an outbound VPN connection to the operator's UNC - not something that the average enterprise security manager would be too happy about, unless a separate partitioned domain could be implemented on the wireless network.
Conversely, most of RIM's other operator customers aren't using UMA, and so presumably won't want to be spending money for lumps of complex software in the stack that will go unused. I suppose it's possible that they could ship with the UMA software 'dormant', though - especially if the per-device royalty was only payable on phones which were actually activated. Whether it'll have some form of VCC/pre-VCC client is another matter - I suspect we might have to wait for dual-mode BlackBerry V2.0 for that.
On the other side of the coin, I imagine that RIM has been keenly aware of the drive for SIP-based PBX-centric dual-mode devices - and conscious of Nokia's E-series and various Windows devices' incumbency there. The lure of unified comms, VoWLAN and possible tighter relationships with Cisco, Avaya, Divitas, Siemens, Varaha and assorted others must be pretty potent. I'd imagine RIM doesn't want to miss out on an emerging market for converged corporate voice/data devices.
But that opportunity comes with a sting its tail - although some of the fixed/mobile hybrid carriers are moving towards managed dual-mode IP-PBX implementations (eg BT Corporate Fusion), there is definitely a strong move towards enterprises buying 'vanilla' WiFi handsets through alternative channels, rather than operator-customised ones.
So.... could the dual-mode BlackBerry make an appearance through non-operator channels? Perhaps sold through a systems integrator, with the enterprise sourcing SIMs and voice/data airtime separately? It's got to be a tricky decision for RIM, given its strong carrier partnerships. But sooner or later, they have to deal with the undeniable fact that some enterprises will want to source all their own mobility hardware (including mobile email servers), and just pick one or more operators as a cellular bit-pipe.