For v11 we'll be doing #2912 instead, the hybrid responsive theme. This is almost complete in a separate v10 branch, undergoing testing and tuning. We'll also be doing the JS overhaul (everything in "Improving the default theme" except the last two bullets), which is mostly completed now. We may also do some flat design work.

The thinking is that the single hybrid theme provides a best-of-both-worlds approach regarding mobile mode and responsive design, without these Bootstrap disadvantages:
- Implementation costs
- Complexity for themers
- Disruption
- Ongoing maintenance costs

Particularly I am concerned about Composr empowering people, rather than dumping an incredibly convoluted set of templates and CSS on people that they don't have the skill to customise.

A future Bootstrap theme will likely be tied to a Patreon campaign based on democratic decisions of what should be the next big development priority (Google AMP would be another contender).