The newer dev builds of Sublime Text introduced a way to render popups (that hover over text) using a subset of html (minihtml). It's already being used to show

The newer dev builds of Sublime Text introduced a way to render popups (that hover over text) using a subset of html (minihtml). It's already being used to show a list of references under the cursor as well as better build errors. I imagine there will be extensions taking advantage of this soon.