I think that the size of the organization has a lot to do with this. I work for a medium growing to large corporation (~6000 employees world-wide) which gives me a totally different perspective than people serving small businesses.
In my company the Telecommunications group is already part of Information Technology (IT) and the group is probably going to get a new name of Network Communications to better reflect what they handle: MPLS circuits, voice circuits (PRI + POTS), home office circuits (cable or DSL), cell phones, conference bridge administration, call center administration, and phone system + voice mail administration. This group uses the same help desk system as the rest of IT, but with a radically different Service Level Agreement (SLA) to make certain that voice problems are prioritized properly.
In an organization of this size, it doesn't seem reasonable to make a blanket statement like, "To have nothing but IP phones through out the office would be cost foolish." Our new IP phones save us a ton of time with MAC work compared to our old Nortel digital phones. Our organization is very standards-based and so we want everything to be the same. We are using our MPLS network to call from site to site around the globe with dramatically lower cost than we did in the past. We moved to the new technology because it benefits our organization, not because we wanted bleeding-edge technology to tout.
In our corporate environment the shift to data HAS already occurred as the OP stated. Smaller companies will move this way as they grow in size or as the technology becomes more robust and cost-effective. There was a time when only big companies could afford a PBX with voice mail in-house. Now even mom-and-pop shops have this technology. The change didn't happen overnight. I think it is reasonable to expect the same type of progression regarding the move to data. If I were serving small to medium sized customers I would prepare for the change rather than deny it.
-Rob
