The article suggests, I believe, you can do it right now with any Android phone too. Sourcing a service is the issue. For some USAnians who choose Android, Google Voice + Cyanogenmod (for the built-in Voice+ app) has constituted that service. (Or will have done for as long as Google Voice stays open.) By "the data-only phone", it turns out I actually mean, what if the phone companies generally offered such a service.
In ze future, wireless data is going to be a hell of a lot faster and also more widespread. Consider the
pCell for instance. Such technologies will open up a big black hole right underneath telco voice and sms services, but in the lead up, in the, say, twenty years it takes to make those things operational and widespread, the telcos will continue to gouge.
What I mean is, I'd actually pay for a reasonable data plan if there were such data-only services. I'd certainly use wifi while at home, and that'd net the telcos nothing, but I'd use their data-plans while out and about, just like I don't right now.
/blue sky