I personally don't think so, but think this could merit some good discussion, and will try to present both sides in limited fashion.
First, I want to point out that I give both the source of the story and author of the email a lot of credibility. I think the email was well written with some well reasoned concerns that need to be realized by the public at large before it is to late. The author of the email thinks that specialized appliances will replace the PC, and there is nothing that can be done about it. It is his opinion that this will result in the inevitable death knell to the beloved PC.
Hale mentions that companies like Microsoft and Intel want to be able to force complete content control and monthly rental fees on something people are used to owning outright. It's why Microsoft is getting rid of the version number with Office XP and it's upcoming Operating Systems. MS wants consumers to get away from the idea that they own something that they have paid hundreds of dollars for.
Companies like IBM, Intel, and Phoenix want to provide hardware that will enforce through technology restrictions that cannot be enforced through law. This is what Hale is working with on the T13 committee, and what could turn the PC into a content control machine.
If anything, appliances are becoming more and more PC like, with technologies like wireless 1394 paving the way to connect them to your computer. Hale proposes that Intel wants the computer to become a "control center" for the house. The PC is not going to be replaced by specialized appliances, it is the specialized appliances that are going to be replaced and controlled by PC's. For example, car stereos for cars. Their now available car stereos that have small computers inside the car stereo chassis (they use laptop hard drives), and these can download data from your laptop or computer through a USB port. Products like these are only going to make the consumer more dependant on the PC, not less.
While Hale points out that proprietary devices like the Tivo could replace the PC. There is no question that the entertainment industry wants to change our entire entertainment experience. Divx was nothing more than a trial for turning the Play button into Pay button. Microsoft wants you to pay a monthly bill to use your computer. Intel wants to prevent you from using computer in unauthorized ways. How can such powerful players be stopped from killing the computer and replacing it with specialized appliances?
There are two primary reasons why that this won't happen. These are the same reasons that allowed the PC to displace terminals in the first place. Economics and Versatility.
Home users like the ability to have one machine that can be used to play computer games, do taxes, surf the internet, listen to MP3's, watch their porn, and so on. Business users need the ability to do word processing, spread sheets, databases, order entry, internet and so on.
While companies like MS can try to force people to have their computer become an independent network appliance (.NET) by only allowing the .NET versions of their OS and Office to be sold, it's going to be harder to do this with business. When most companies with greater than 250 users get a computer, it is imaged upon receipt with their OS of choice. Overwhelmingly this is W95, not the latest that Redmond has put out. Corporations and consumers have grown used to the versatility of the PC, and cannot economically afford to lose that versatility.
Like corporations using the well known W95 on desktops, people will go back to what worked before. For example, when New York instigated new toilet standards, the price of old toilets within several hundred miles of New York jumped through the roof. The new product was unacceptable (didn't flush everything), and people went back to the known standard that worked.
I don't see any reason why computers will be any different. If you make things too much of a pain in the ass for Joe Consumer, Joe Consumer will decide to take action or ignore the rules/law in mass. This has happened with prohibition, pot, the speed limit, and will happen with computers if things become to inconvenient for Joe Consumer. This is what can create a public backlash, if the backlash is strong enough, politicians will listen.