Some observations
It's interesting how some of the Windows supportes haven't tried Linux, even when they say they have. What is that all about?
I don't use Windows at home so I can't comment on how difficult it is to do specific things. I can, however, sit down at a Windows machine and browse the net or write a document, in the same fashion that I do on Linux. Why would that be any different? There are a lot of similarities. They are both following some popular mythical concept of how things are "supposed" to be. Specifically, the use of a complicated picture like GUI, the use of a pointing device requireing hand eye coordination and other unnescesary resources, and the insistance on using a "desktop". In general, making it look and work like some kind of game. (I hate games with a passion.) These concepts have contributed much to taking control away from the user and making "personal" computing a thing of the past. In Linux, if you want to do somehing in a non automated way, it becomes very difficult. Not because of the command line (that's easy for anyone who can type) but because the system is so complex. Even making small changes to my setup is beyond me. Such simple things as colour of various elements, and placement on the screen, require more skills than i am prepared to acquire. I am stuck with using applications to get anything done. I didn't use to have that problem with DOS and I'm still waiting for Linux to catch up ... but I don't think it will. Linux has gone off on the same tangent that Windows and everyone else has. The blind, unimaginative, insistance on using that stupid concept called "the desktop". This is now a world of pre done, no choice, applications only, computing. Most computer users don't actually touch the OS.
I really don't think it matters much what OS you choose, the average user is going to get the same lack of control. Where the differences lie, is in the attitudes and politics. My computing problems would probably not be be solved by moving to Windows, but I would be into a world of questionable ethics which I don't want to be part of. That's why I stick with Linux despite the problems that I have with it. More people are starting to think the same way.
PS: The title asked if Linux could (not would) become dominant. Yes, I think it "could", but it very well may not.