I'll sidestep the PC gaming issue, simply because that the idea of the PC itself being dead was more interesting. Valid points made, but there was a concession made about how Bob would only need his PC for video creation. That scratches the tip of a whole 'nother iceberg.
If you're going to do any high-resolution video production (especially at the professional level), I personally don't look at a laptop and say, "Yeah, I want to do my editing and rendering there." I could be wrong - maybe half of the film-making world has moved to running Final Cut Pro on their laptops - but that isn't the only thing people go to PCs for.
Take animation for example. For all the time it takes to create, animate, and render 3D animations (especially production animation, like for video games and films), do you really want to dedicate your personal laptop for all those hours of processing? Wouldn't the animator rather leave it to a slightly more powerful machine that's less likely to be carried around?
Not to mention the applications of PCs in the business world. Companies that rely on heavy-duty computer technology (film studios, animation companies, software developers) are quite likely to have a series of on-site workstations for their employees to use, connected to a repository server network they control. It's far more convenient and secure for everyone involved, given the work that has to be done.
A lot of that doesn't really involve the "Personal Computer." I realize that. Maybe the "PC" as we know it will simply turn into the "Workstation." But I don't think the form of this technology is going to fade away anytime soon.
And besides, the video brought up (and immediately discarded) the whole social/casual game market that will keep people glued to their computers. But that's enough arguing for me.