Actually, that sounds like UMA which has already been deployed by BT first using a bluetooth basestation in the home now having been upgraded to WiFi. Since there are already UMA phones in production and the UMA standard has been ratified by the 3GPP I seriously doubt that InStat even knows about Calypso. I read their reports recently and while there was plenty of discussion on hybrid handsets that utilized WiFi and GSM in tandem as well as mention of UMA, there was not one word on Calypso.
One thing to keep in mind is that any seamless switching solution that sits at the edges of the network will be by default much more expensive to deploy and much harder to maintain.
Why? If you're talking about end-points, that means the base station is handling the handoff from the cellular tower to the IP network whereas if a controller at the network core does this, so long as the handset registers on the cellular network AND the basestation that information can be passed to the core where the networks converge; this supports the fastest handoff.
Ask a carrier which they'd rather support, centrally managed devices that handle registration, authentication and billing or customer premesis equipment that has to be installed, and which will cost a fortune to support and which is also constantly vulnerable to consumers with screwdrivers and a few "ideas".
-stitch
