Heh, people have been predicting the death of the pc for 20 years and it hasn't happened yet.
I think PC's now are similar to the way cars were in the 50's or 60's (I think, I wasn't born until '71, so what do I know); the enthusiast market is driven because people like to tinker and tweak and customize, kind of how I think cars used to be (and still are, to a certain extent). And that market is HUGE. All you have to do is look at the number of different motherboard makers out there. There're dozens!
Think of how many people are terrified to mess with a computer, but there are so many people out there perfectly comfortable replacing motherboards, chips, memory, drives whatever, that it drives an entire industry. If there wasn't a market for it, there wouldn't be all those companies out there. Everyone would just be buying Dells.
I do not think a significant part of this market is going to completely give up PC's and buy Xboxes or PS3. I think they do it because they like it and they're not going to quit. As long as they're there, there will be games made for them.
And it's yet to be proven to me that pc games are inferior to console games in any way.