There Is No Shelter
Of course, the same arguements could be made in regards to the iPhone. It was and remains an incredibly competent product, yet Android based Smartphones have managed to become the market share leader. This is often used to justify the idea that Android will also come to dominate the tablet market.
There are major differences between the tablet and smartphone market, however. The most important is the lack of carriers. Smartphones are useless without access to mobile data, and that must be provided by carriers, who certify certain phones for use with their networks. This limited Apple's market reach in the past, and will continue to do so in the future. As a result, Android was able to mature in a sheltered environment, protected from the iPhone by virtue of the fact that a majority of the market simply could not purchase it for use on their carrier.
Although tablets can be used on mobile data plans, they are not restricted to any specific carrier and many are limited to WiFi. The majority of potential tablet consumers can go out and buy any tablet they'd like - which means that all tablets are in direct competition with each other.
In addition, the smartphone market could never be cornered by Apple, as I explained in the first section of this article. It's too large and diverse, which gives room for competitors to survive and thrive even when their initial offerings aren't on par with what Apple offers. The tablet market is and will be smaller, leaving less room for competitors to carve their own niche.