Apple's VoIP hires are about working with the carriers, not leaving them2
To be sure, this isn’t a wholly crazy idea. Steve Jobs explored the possibility of shirking the carriers altogether. Google is also rumored to have dabbled in the idea, and the original idea behind the Nexus One retail strategy was to disrupt the carrier pricing strategy, although it didn't work out well for them.
In short, lots of tech companies have looked at ways to help reduce the carriers to dumb pipe companies; such a move would be immensely beneficial to consumers, as the carriers charge fees for voice and text messaging that are far higher than the data cost would justify. That’s why carriers restricted (and still restrict) some VoIP implementations on smartphones, and why they chafe at iMessage and other data-based texting apps.
But, as GigaOm has pointed out, this hire is not evidence that Apple is finally going down this path. The job posting specifically asks for “experience in SIP, real-time transport protocol (RTP), and VoIP related protocols…familiarity with telecommunication network architectures: GSM/UMTS, CDMA, VoIP, IMS."
If you aren’t familiar with all those acronyms, the key here is IMS (IP Multimedia Subsystem); IMS is a standard that is being implemented by many of the world’s largest carriers to bring voice communication over LTE. In the U.S., three of the four major carriers either have, or have committed to implementing voice and text services using IMS.
IMS is a carrier-driven standard, and it comes with a lot “baggage”, the kind of legacy support you need when you have to maintain backwards compatibility with everyone’s phone. It’s almost certainly not the type of standard that Apple would choose if it were going to build an iPhone-based VoIP network. It appears instead that Apple is looking for engineers to add voice over LTE capabilities to iOS (presumably for upcoming iPhones), which is somewhat exciting in and of itself.
source: Apple job posting; GigaOm