No. I've been through the last year's cycle, but it doesn't really hurt even a little bit if you take the test in October. But, it will help you a big time if you start learning the app process and preparing for the LORs and personal statements right after the October test. I emailed many schools about the advantage of June test takers - some of them said there's only a very slight advantage. Most said there's no advantage.
So, the verdict is.. if you don't have much to do during the summer, and you're scoring in the range of under 170, then it's better to take the test in October.