I'd be really curious about that breaking change since we really want to not do that, so if it happens, even in a loophole then we should know about it. Either we make an internal policy that says.. we don't support loopholes, or we get very strict about not breaking those things. But I'd love the input. To answer your question: in theory we wouldn't be making breaking changes, only if you must support a new feature that doesn't exist in 9.0.0 I would bump the version personally.