I've been hearing that this winter in the Midwest (remember that I'm in St. Louis) has a high probability of being a mild one. As a zone 6 bamboo grower I hope for a mild winter every year, as it's important for the plants to keep their green leaves in order to have any chance of a "size up" next year -- meaning larger, taller culms emerging in spring.
The last two winters were tough on bamboo here. Two winters ago was the worst, when all of my plants defoliated -- you can see the results in the image above. At -8ºF (-22ºC) I was literally one or two degrees away from "topkill", where even the culms are killed -- probably the worst-case scenario for bamboo lovers. The winter before that (which would have been 2012-2013) was quite mild though -- is this what I should expect for 2015-2016?