Android is taking off and Meego is on it's way, The Kno tablet runs Ubuntu and Google has released it's Chrome OS. All four of the operating systems listed above are Linux distributions. I believe this is only the tip of the iceberg. It is obvious that operating systems today are far more complex and capable than they were in the eighties or nineties. As consumers expect more and more from their phones and tablets, the OS those devices run must be able to handle that demand.
Say company X wants to start selling tablets but they don't have an OS:
Option 1: They hire some developers and start making one. After years of expensive development, they have one that can do what other OS's could do ten years ago and no applications.
Option 2: They buy and OEM license for a proprietary OS. Now the device works, but looks and acts exactly how it was made to look by the third party company. Company X cannot change anything about the OS. Which limits them significantly, plus they have to pay the third party company a large chunk of their profit and raise their prices to compensate.
Option 3: They use Linux. Either an existing distribution or their own fork. They have absolute control over everything, (as long as they release the source code), keep 100% of the profits and don't have to do much or any development.
Put that way, the correct choice is clear. That makes many of use Linux fans very happy. But should it? Here's the bad news: the freedom that Linux provides is limited. The absolute control that we have over our Ubuntu, Debian, Arch, and Fedora systems, (to name a few), will not necessarily be duplicated in Company X's tablet.
As many Android devices have proven, whoever installs the Linux system can easily set the root password and lock down whatever features they don't want their customers to access. And when the device is embedded, it is really hard to get around such things. It can be rooted, of course, but an iphone can be jailbroke.
The bottom line is this: get used to Linux, it's going to be around much, much longer than any of us, but don't settle for the kind of crap companies have been selling. Buy products that give you control.