Wow, the comments are just flooding in. I can't read fast enough to keep up, so I'll just say this:
The issues for me have always been customization and preference.
First, I'll have a PC as long as I can put it to a wide range of tasks, and tinker to satisfy my curiosity. Also, most of the games I enjoy have a wide array of user-generated content that is only available on the PC. The most recent commercial for Little Big Planet 2 touts the 'mind blowing' option of playing thousands of user created maps on the console, but compared to the content and mods available for game series like Fallout or The Elder Scrolls, it just scratches the surface.
Second, I don't care much what platform I'm using for games as long as it suits my preference. I enjoy certain games (like shooters) on a console because I don't need a mouse and keyboard for them, and it's more comfortable to play from my couch with a controller. On the other hand, some are better sitting at a desk (like MMO's), because they require a more complex interface which is easily accessible when sitting upright.
Would I like to play more games from the couch? Sure. It's getting easier to do this with cross-platform titles. However, I do enjoy the variety of going back and forth between PC and console since it gives me a different perspective and experience while playing games. I don't know if I could ever see myself playing all my games on a console, or all on a PC, even if technology and my setup of furniture allowed for it. It's always been this way for me, even when consoles were much more different from PC's than they are now, but that's because I'm invested in both.
I would agree that PC gaming *as we know it* is in decline. What we consider to be 'gaming', and who we consider 'gamers' is changing rapidly, so it's really hard to say what place PC gaming will hold in decades to come.