Motorola Mobility’s Ninja HTML5 framework, that was unveiled mid-2012, however without new references since many months, was replaced by Google Web Designer, an Adobe Edge/Apple iAd Producer like HTML5 ads builder, then with limited scope (no more a rich internet applications builder). The Montage HTML5 framework (that was the basis for Ninja HTML5) is still available (open source).
We can find more details in this greatly written article, that underlines that there isn’t any HTML5 web applications solution (framework and builder) available (GWT is old, not HTML5 focused and no more driven by Google), only basic tools and low level frameworks (jQuery, angularJS, BackboneJS, Twitter Bootstrap).
We can however still use Cappuccino and Apple’s XCode/Interface Builder to build applications such as emotuned.com or direct2it.co (using Direct2CP’s solution mda approach allowed building these easily even without IB).
In fact all single page/anonymous div based frameworks can easily use HTML5 features when required, by extending existing components. That is adding/generating new doms elements (and/or new css values) to components. Cappuccino still uses CSS3 for Popover and other areas, while Direct2CP components wrap HTML5 audio and video tags (also use CSS3 animations) and new upload features.
Then a whole new HTML5 framework would not provide more (as many features aren’t HTML5 specific), at least a true HTML5 framework would be replacing all anonymous divs by WebGL elements (that is wrapping these in components) for rendering (HTML5 also provides features that aren’t display related, like storage).