Today the first development build (pre-release) for 2.7 has been made available. It can be downloaded, in one of three flavours, from these links:
In general, it's recommended to use the Advanced or Traditional builds. Traditional is the standard build, advanced allows you to more easily rename the core directories during the setup, and SDK is useful for addon developers as it comes with additional uncompressed versions of the ExtJS library that can make debugging easier.
It's expected that new builds will be made available ahead of the stable 2.7 release at the end of the month. When that happens, we'll update this post.
Curious about what's new in 2.7? Check the 2.7 changelog here.