I do not insist about blocker status, only if you and the Team think it should be. I personally agree that broken layout switching is unacceptable for majority of non-US users and should be addressed as top priority.
It is also proven to be so by poll/post about what people want in R4.2.
And if you do decide to use blocker for R4.2 than this issue can be used as one that describes the problem in general. Of course, this issue affects-4.2 at the moment, I believe.