Nope. Hardware sales are projected to decline very slightly over a couple of years and then start to return. For a market that is constantly under the claim of "dying", they sure are selling an awful lot of $1,000 video cards and $300 CPUs and $300 chassis' and making whole businesses out of catering to even more niche markets like water cooling nuts.
Steam has 65,000,000 users. That is more than XBOX (but less than Playstation). That's not PC gamers. That's just *Steam* gamers.
Consoles are $300-$500. The lowest end gaming PC that you can get by with starts at that price. Further, games have largely been targeted at consoles and ported to PCs in such a way that they just don't really demand much of the PC hardware.
In other words, PC gaming is as big as it has ever been. Even if mobile and console platforms grow massively, that doesn't detract from PC gaming. You can do more than one platform. It's just that software necessitates the increase in hardware capacity and software just hasn't been making those demands for a long time, leaving PC gamers to make longer use of their PC hardware. That reflects in hardware sales. A reduction in hardware sales means just that - a reduction in hardware sales; not a reduction in people playing on their existing hardware.
Additionally, we've been told for years now that *console* gaming is dying and will soon be dead. And so will all handhelds that aren't a tablet or mobile phone. Of course, that is bullshit. Steam's user numbers, the popularity of PC-only games, and the 8,000,000 PS4 and XB1 consoles sold in the last two months is evidence that it is bullshit.
I am skeptical about the future of PC gaming, but not because of some perceived lack of interested gamers. The only thing that can harm PC gaming is if developers and publishers continue to treat PC gaming like a redheaded stepchild. If they continue to put out PC ports in a half-assed and often-broken fashion and months or years after the console versions of the same game. And if they continue to not exploit the power of the PC, but just port over console versions of games that look and play progressively worse over time as the console platform ages.
If PC gaming dies, it won't be for lack of interest. It'll be because it was sabotaged and undermined by the developers and publishers.