According to the NPD Group, North American retail sales of PC games came to nearly a billion dollars -- $910.7B -- in 2007. And that's not including sales through digital distribution.
A billion dollars in the N.A. retail market alone suggests that there's additional revenue to be found in other regions whose use of general-purpose computers is still growing.
And there is no sign that the market for general-purpose computers is drying up worldwide. As long as there are general-purpose computers, there will be good business to be done in making and selling games for those computers.
Even so, it's clearly not wise to assume that the mere existence of PCs is enough to guarantee the continued sales of PC games... not when console manufacturers are doing everything they can to make consumers (and retailers) believe that all the cool kids play their games on consoles (and handhelds), not PCs.
People have accepted the self-serving "the PC is dead!" comments by game console manufacturers as truth because no major PC hardware manufacturer has been equally vigorous in promoting the PC as a game platform. Perhaps the formation of the PC Gaming Alliance, along with Intel's purchase of Havok and game developer Offset Software, are early signals that those with a stake in PC gaming are finally ready to defend the value of the PC as a worthwhile platform for gaming.
That's not a crazy idea at all.