Surprisingly it doesn't, I imagine that's because there's always a demand for gems, and seeing as there's so many people that sell ore they're always trying to undercut each other so theirs will sell which kind of works out really nicely for making gold

As far as being useful in the future, this guide should continue to be relevant during every expansion blizzard releases unless there is a major change in how professions work, although you may have to wait a couple of weeks/months after expo releases for the economy to stabilise a bit!