Hmmmm.... no.
This rant is so confused I'm not sure Bob knows what he's ranting about.
I guess it boils down to: "The days of people buying $5000 rigs to play with the highest possible framerate are over."
To which I say: "No, you're probably wrong about this."
Yes, this will become a less popular option in the future. Except that it was not a particularly popular option to begin with. Most people just go to Best Buy, grab the $200 computer, and let that be the end of it. Some might go a little higher in cost, but for the most part an ubergaming rig was a fairly hobbyist move.
Of course that's not what we're talking about, because Bob has decided to define PCs as Desktops. And yeah, desktops are quickly falling out of favor with plenty of people. A laptop is simply more mobile than it's fixed-location competitor, never mind the other options listed. A laptop is also a personal computer, or PC. That people have gone to great lengths to willfully confuse PCs as Windows desktops does little to actually define it as such. Just like saying "supposably" over and over doesn't actually make it a word.
But let's address his statement directly, and see why it doesn't hold water:
1. Ubiquity
I have pretty much every console in the current generation. I like my consoles. But, for the most part, people are generally limited to one, maybe two consoles. Never mind that these consoles are massively incompatible with each other. Everyone and their grandmother has a PC, however. Not all of them are graphical powerhouses(hell, probably some don't even have a GUI), but the general omnipresence of a Personal Computer in every household makes it a pretty difficult market to ignore. Most of the Greatest Generation, Baby Boomers, even a hearty dose of Gen-Xers may not be a target. But they have kids and grandkids, and such progeny may not be able to sway the hearts and minds of their breadwinners into buying them a whole new vidja game console. So they have to make do with the one outlet they have: the computer.
What's more is these supposedly dying vessels of entertainment pretty much all share a common hardware architecture. Developers are more comfortable developing on them, a lot of the APIs are the same, and there's just an awful lot of inertia to overcome. Throw that in with distribution channels that not only allow people to easily purchase and acquire such games, but allow them to make multiple installs without multiple purchases(hey there, steam!), and you've created a pretty attractive platform for development and distribution.
2. Upgrades
Yes, most people don't like doing this still. However, take a look at GDC this year. Crytek engines, Unigines, whatever B:BC 3 uses. Developers have reached pretty close to the end of what the consoles can do, and yet it's years before the development cycle is over. Meanwhile, other tech is scrambling to establish dominance. And the easiest(and often most effective) way to do this is by proudly touting graphical superiority. That's pretty damn hard to do when everyone already uses the Unreal 3 engine. And granted, most of these engines scale downward, but there are gamers out there that still are bubbling with desire to purchase the latest and greatest, visually speaking.
That isn't to say that consoles don't receive upgrades. I don't see many NES games in Gamestop anymore. But each upgrade involves a radical change in architecture, APIs, often the spurning of backwards compatibility, and so on. While they do make steps towards allowing the systems to perform more tasks, they don't multitask, and their interfaces are TERRIBLE when it comes to conveniently accomplishing day-to-day tasks. Computers are simply better at doing these things, all while playing video games.
All right, enough with the listing, I hate replying by numbers. The point is that there's very little evidence to back your claim. There's evidence that handheld devices are becoming more popular. There's proof that casual gaming is a much bigger cash cow that hardcore gaming. And some publishing execs have even extolled the virtues of smaller, more convenient platforms, such as consoles, handhelds, and smartphones. But these are largely arguments against the hardcore games in general, not PC gaming. Meanwhile, let's look at what PCs are up to...
Blizzard is still kicking ass, taking names, and making sales, all the while supporting that extremely costly blister that is Activision, who's recently lost control of Infinity Ward, canned Guitar Hero, brought the Tony Hawk franchise to utter and complete ruin, while pouring more money into the bottomless pit that is DJ Hero. All while wasting tons in their various litigious actions.
Valve runs Steam, which is fast making them one of the highest profit-per-employee company in the software industry.
Dice is making Battlefield: Bad Company 3 with the PC in mind, secondarily porting over to other consoles.
Unigine is not only making its mark in the graphical world, but also doing a fair job encouraging cross-platform compatibility, further cementing its place in the gaming world.
The point is that PC gaming may not be the juggernaut anymore that it once was in hardcore gamers' heads. But that's a far cry from "the writing's on the wall."
I guess a faster way to respond to your statement is: [citation needed].