To implement responsive web design and to clean up and unify Tiki's CSS classes, we are integrating the Bootstrap CSS framework into the upcoming Tiki 13 release.
With this change, producing a theme for a Tiki web site will be as simple as generating a custom bootstrap.css file. Bootstrap theme files for other blog or CMS platforms will be able to work with Tiki more or less, depending on the degree to which they rely on native Bootstrap CSS classes rather than theme-specific HTML. The best existing Tiki themes will be updated to be Bootstrap-compatible, and there will be documentation to guide others wanting to update their older themes.
Find a list of the members of "Team Bootstrap":
Bootstrap Team on tiki.org
More about Bootstrap framework: getbootstrap.com
We are currently doing testing on a show.tiki.org instance - http://pascalstjean-10536-4949.show.tikiwiki.org - that uses the Bootswatch.com's "Amelia" as the default theme. This theme contrasts well with native Tiki elements and was chosen to facilitate testing.
There is also another site running Tiki Skeleton theme to be able to test various elements in a cleaner environment: http://pascalstjean-10536-4948.show.tikiwiki.org.
The bug tracker being used for Bootstrap issues is themes.tiki.org's tracker2.
Some reporting from the Montreal and Ottawa TikiHouses: TikiFest Blog (mostly summarizing the Big Blue Button sessions).