I keep reading about studies that claim the PDA is dead. However, whenever I look a little more closely, the article claims that PDAs are losing ground to smart phones (not Microsoft Smartphone, but the product category smart phones).
As far as I can tell, they define a Personal Data Assistant as a "device that stores contact, calendar, and task data, perhaps can run some applications, and has no connectivity. In fact, they appear to explicitly exclude MP3 players from the PDA category.
Apparently, a device can be a phone if it has PDA features, but it can not be a PDA if it has phone features. In other words, PalmOne's Treo series reduces the market for their disconnected PDAs.
So it isn't terribly surprising that "the market for PDAs is diminishing", using this artificial definition. However, it would be more appropriate to say, "more users are demanding that their PDAs have wireless voice or data connectivity" and that after the next few years most or all PDAs sold outside of niche markets will have connectivity.