This argument has been around for at least 20 years, I'd say. I remember reading in the 1990s how within 5 years the home computer, TV, VCR and game station would all be merged into one multifunction appliance. What has really happened is that each of these appliances can do many of the things the others do... and we still have them all in our homes. Not everybody has them all, of course. But none of these things has disappeared (well, the VCR yes, but it was replaced by another technology, not by a do-it-all device).
Yes, for occasional users and low-end market segment, there is some truth in that, as some have said here already. But the overall trend is not toward consolidation of all functionalities into one device. Quite the opposite in fact.
Right now in my handbag I have a 3G smartphone, an iPod Touch (I know, I know, but I was too cheap to buy the iPhone
), and my Opus. Will this change in years to come? Certainly, but I'm not sure the number of devices will be reduced. I certainly can't see myself using an Opus-sized device as a phone, or reading on my smartphone's tiny screen. I only read newspapers on the iPod, and I could never finish a book on it, though it did come in handy when my e-reader went on the fritz last summer.
Anyway, that "X will replace A, B and C too" idea is something I have never believed, and never seen so far.