I think citing DistroWatch to get an idea of popularity is completely inaccurate. It may be okay as evidence for what newer users are interested in, but a lot of people go directly to a distribution's website instead of going through another website. I highly doubt Arch, Fedora and Gentoo users visit DistroWatch. There's also the fact that plenty of companies use Red Hat, Suse, CentOS and other in-house distros. I love Linux, but I don't think it will see exponential adoption growth any time soon considering how much of the community wants to do things their own way instead of coming up with a common solution. It's the paradox of choice, really.