Several years ago, TGC announced Freedom Engine, which used the same code base as AppGameKit but was web-based. It allowed creation of WebGL-based apps. Unfortunately, it never left the beta stage and I think it was ahead of the time due to the limited scope of WebGL in browsers and hardware (most other HTML-based exporters at the time rendered using HTML5 canvas which was already well supported). A lot has changed in three years time so it would be interesting to resurrect the HTML/WebGL export capabilities within AGK.
Having said that, I don't know of any immediate plans to support HTML5. Their original roadmap from 2011 mentioned HTML (and Windows Phone) as future platforms but it hasn't happened yet.