We are looking to release 2.0 soon after WordPress 4.0 is out, which means end of August/beginning of September. I'm testing with 4.0 beta right now and things look good so far.
The release will be an update to Thematic and be available through you site's dashboard and here on wordpress.org. This is why we want to test it properly, so no sites will break in the upgrade.
In the final version there is no checkbox for html5 markup in the theme options. New installations will get the html5 markup with responsive styles automatically.
And yes, you should be able to continue to use your child theme with the stable release. That's the whole idea. Just upgrade (replace) the parent theme files.