Switching to Java 6 to Java 7 has nothing to do with language
The problem for most companies to switch from Java 6 to Java 7 has nothing to do with changes in the language, but mostly with having a new version itself. I am not aware of any language change that is not backward compatible (as in code written for Java 6 will still work in Java 7).
Most of the problems are with resistance to change or lack of corporate reasons to change, and platforms that only (formally) support running on Java 6. Also for some reason companies are a lot less weary of updating point release than updating to major release. Add to that the lack of exciting new features in Java 7 (with the exception of try-with-resources), and there is no real good reason to spend time and effort to switch.
All-in-all Java 7 was a disappointment, and now it looks some of the exciting things which mere delayed to Java 8 will be delayed to Java 9....