Someday Linux desktop percentage will jump up, but not how the optimists have thought. It's going to be more because the younger generations don't think they need desktop operating systems, leaving them exclusively to to younger gen-X, older gen-Y, various hobbyists, and those who need a desktop workflow at work and like it enough to bring it home. The desktop will settle into its niche, like live theater, fountain pens, and a thousand other mass culture relics, and Linux will still be there chugging along while Windows and OS X (as we know them) slowly molder due to reduced profits in the desktop space.
I have a kid, and yes, there's a laptop she uses, but to her it's exclusively for games and for dicking around in Roblox Studio or TinkerCAD. I've even seen her close a game, settle into her chair at the very same desk, and pull up Youtube on an iOS device. And this is from a kid who is more comfortable with a PC than most of her peers.