1. Yes, as a backer you'll get access to all the updates for this course content. I will fully support iOS 7 and Xcode 5 after they are public in the fall.
2. The initial course content that I publish for BETA backers will be targeted at iOS 6.0, and I will use feedback to revamp the materials for iOS 7. A lot of the basic coding won't change, but Xcode 5 means I'll need to redo the videos that demonstrate how to use Xcode.
3. 92% of iOS users are running iOS 6.0+. It makes sense to only teach the latest tools for new developers because you can make apps faster. There's less code to write and things are easier to do.