No, I don't think PCs are dying. However, I do think Desktops are dying. The majority of people that I know that have purchased new computers did not purchase desktops. Also, they did not purchase Macs (although I have a strong desire to buy one ). They purchased notebooks. I see more and more people buying notebooks.
You only need to walk around almost any airport in the world to realize that PCs are _not_ "on the way out." In my travel to Singapore and Amsterdam recently, I lost count of how many notebooks I saw people using in airports. And not just geeks. I'm talking about kids, grandparents, etc.
I do think that computers are becoming more media-centric though. Most "normal" people I saw in airports on this trip with laptops were watching DVDs or playing video games on them.