Another niche for the html/css guru that is still valid is the ability to really customize something like twitter bootstrap. Anyone can throw together a site using bootstrap but actually wrangling it to look unique is another challenge in itself. You really need to understand css inheritence and how use the real power of the framework. Not to mention using 3rd party bootstrap plugins and customizing their look and feel to fit your theme. The ability to skin any framework or cms that has templating is a valuable skill to have.
