I'm not particularly afraid of that, as long as people are still buying full-size gaming rigs they aren't going anywhere. It's like the Small Block Chevy, even decades after GM stopped building them, there is a tremendous aftermarket community that manufactures new and improved parts for them.
The thing is that, as long as Moore's Law keeps up, desktops will eventually be outperformed by laptops for anything that doesn't involve massive parallelism or high redundancy requirements. There's a reason that mainframes and minicomputers are no longer popular: Performance increases in computing come from miniaturization. For a given size, there's a maximum performance you can get, limited by the length of your signal paths. Sure, there will probably be *some* market for desktops in the future, but quite possibly not for the uses you might expect, and in any case, you'll lose the economies of scale that desktops now have. Even now the advantages of a laptop are considerable enough to offset the extra price for enough people that they outsell desktops. If Moore's Law continues to hold for long enough, the time will eventually come when the desktop hits a point of diminishing returns and ceases to even be price-competitive. (Of course, eventually Moore's Law will run up against hard limits in semiconductor technology. If a new technology cannot be found by then that can make similar exponential performance gains by miniaturization, none of the above will apply, and there's a chance that that will happen before desktops hit that point of diminishing returns).
So eventually people will stop buying desktops because they cease to be competitive price-to-performance-ratio-wise.
Even though computing in general seems to be trending to locked-down, Fischer-Pricey tablet interfaces, as long as people still buy full-size gaming PCs, the hardware isn't going anywhere. Right now the hardware is cheaper and more accessible than it's ever been.
But even PC hardware is trending toward lockdown. You've got UEFI and secure boot coming in, and while that's not a concern if properly implemented (allowing the user, rather than the manufacturer, control over what operating system signing keys the firmware accepts or rejects), the trend seems to be toward an implementation that is cause for concern.
While it's not (yet) the "everything but Windows will be locked out" that some in the free software crowd have been panicking about, it does seem that, for many machines, only Windows (and maybe one or two more select OS's determined by the manufacturer) will be able to take advantage of secure boot, with users being forced to disable the feature to run OS's of their own choice (and to keep flipping between having it enabled and disabled to dual boot). And I find it a fairly good bet that, if firmware that does allow the user to arbitrarily approve or deny signing keys does show up on the market, computers with it will be priced predatorily high.
And I won't be surprised if Microsoft's marketing department doesn't take advantage of that: "Linux is not secure because it does not take advantage of the secure boot feature of UEFI, whereas Windows does", when really, Linux can take advantage of secure boot, but would just be running up against manufacturers not selling machines without user-configurable secure boot.
---------- Post added at 15:30 ---------- Previous post was at 15:00 ----------
But the topic at hand is starting to creep into my life due to my kids. The usual Nintendo DS is already behind us, I guess the next will be some bigger console. And I think this is one segment of the market you can't easily occupy with PC games: children.
Neah... Me and my brother were into our teens before we ever owned a full-up console at home, and I was in middle school before we even had a Gameboy. All our childhood gaming was done on a PC (and much of it on an old 486 at that). Now, granted, none of our games were the big-name titles you find prominently displayed in stores: they mostly came out of shareware packs, but they entertained us quite well through our childhood.
Now, we may have been atypical children, but I think (though it's purely a semi-educated guess) that a Linux PC might help defray costs that you might otherwise spend on consoles: a lot of the games that are available for Linux are in the same vein as those shareware packs we played as kids (but free full versions instead of demos!). Such games are available for Windows (in fact, I got into the FOSS scene at first through FOSS games and utilities for Windows), but involve more websearching effort to find, as Windows doesn't have much in the way of centralized repositories (except Steam, but I'm not familiar enough with its content to know if it has a large number of titles in the vein of those that entertained me as a kid, plus I don't trust commercial repositories not to implement perverse DRM schemes).