From the authors profile page:
"Farhad Manjoo is Slate's technology columnist and the author of True Enough: Learning To Live in a Post-Fact Society."
Edit: I really feel that any person saying X is unbeatable, is really underestimating competition and the drive to improve what they make.
The iPad at this moment is the best tablet overall, but it won't be long before someone is able to match the quality, and surpass in features. I think what really will clinch this is that once Android tablets come out in force, there will be so many options the iPad will be lost in the noise. This isn't to say the iPad will be the only right choice in that situation, just that when there are options, especially cheaper options, people tend to shop for what suits their needs at a price they can stomach.
The iPad is still too much for most consumers. I myself cannot justify the cost for a consumption device, not to mention how I dislike Apple's handling of their app ecosystem.