This argument is so tired. FOSS is all around us, and getting stronger while commercial software (like Unity) gets crappier (in one way or another).
True, Linux hasn't made much dent in the desktop market. And yet, my household currently has 2 Windows PCs, 1 Linux PC... and at least 10 Linux-based smart devices. Linux is creeping in everywhere, because its openness makes it fundamentally better to work with than commercial platforms.
Many other FOSS products already hold at least enough market share to put pressure on their commercial equivalents to be less evil. I rely on Inkscape where I once used CorelDraw and Illustrator. And I use GIMP extensively as well. It's already ahead of Photoshop in some ways (apart from price) and evolving steadily. Soon it will leave Photoshop behind in the dust - and/or force Adobe to give graphics professionals a better deal.
I also use endless FOSS utilities for digital 'odd jobs' - KeePass is a good example. I use these products not (primarily) because of my belief in the principles of FOSS, but because open standards are practically the only worthwhile guarantee that a product won't abruptly turn against me - as Creative Suite Cloud has done, and as Unity is currently trying to do (to developers).