Honestly, I don't particularly care if linux becomes the desktop of choice among the masses. I only want a large enough user-base that all the major vendors give us as much support as they do Apple, so I can flash my BIOS without using FreeDos, or watch friggin' abc.com.
But as far as it goes, I don't think GNU/Linux will ever get mass adoption until it becomes common place in schools. The only reason people find linux troublesome is unfamiliarity. If you used linux in grade school, and were able to buy linux preinstalled on computers, there would be no more trouble than with Apple or Microsoft. Probably quite a bit less than with Windows, since you wouldn't spend so much time fighting off malware.
Also, the more "user-friendliness" is pushed, the more the integral flexibility and power of the system is compromised. Looking at Macs for an example, you have a Unix-based system that is utterly locked down. Yes, you have a nice user interface, but I couldn't stand the rigidity. Also look at some of the dumbed-down netbook distros like Linpus Lite, where access to the command line and package manager are disabled by default. I suppose from the perspective of Acer as a company, it makes sense - if you have those enabled, it becomes very easy for the novice user to break their machine. In the desktop OS sphere, it's a very delicate balance between maintaining the flexibility and power that so many of us love, and having a clear, easy interface with which to interact with the system.
As far as being able to walk into a store and have a huge linux section...well, distro-wise, that will probably never be the case, since broadband internet is becoming so ubiquitous and it's free to download almost any distro, but walk into any good bookstore, and there is often a pretty significant section dedicated to linux and unix, and the magazine stand usually has at least half a dozen linux mags, with discs included.