I dont know if Linux ever will take the PC market stranglehold from Microsoft, for years now I have ventured to linux periodically to see how things are maturing, but I almost always destroy my Ubuntu OS within a month and head straight back to windows. I consider my self quite technically minded (far more so than general users). And with all the different linux builds and distros etc there's too much variability, most people need reliability and consistency over the ability to tweak their OS to hell and back.

HOWEVER! open source future most likely lies with handheld and niche devices, they can quicker impliment specialised UI's. For touch screens/surfaces/ mobile devices etc. and as mobile computing becomes more and more important, linux saturation in these emerging devices will mean that almost all general consumers will have an open source encounter on a daily base (Weather it be their netbook/mobile/car AV system etc) but not so much their main home computer