Smartphones *OR* PDAs?

The bottom line is that high visibility moves such as the Treo 680 announcement will not only accelerate the growth of smart phones, but also hasten the decline of the PDA.
While Bert Latamore rebuts:
I believe the remaining high-end PDA users are more likely to move to a next-generation PDA than to a smartphone.
So the former believes that PDAs won't die, because power users will still want them, while the latter thinks the smartphone's dropping prices will speed the demise of the PDA. Who's right?
Whoever is, they seem to forget that while the Treo 680 is a gsm smartphone, it's also based on the Palm OS, which in my opinion is first and foremost is a PDA OS.
Wait a minute! Is it possible to determine whether a gadget is a smartphone or PDA by looking at its OS?