AIR 3.2 does now have support for displaying the proper iOS language on the App Store.
You need to include the follwing tag in your -app.xml to support only English. It should be included immediately after your ending </initialWindow> tag.
If you want to support multiple languages, IIRC you include them all in the same tag each separated by a space.
Here are some additional details (also read people's comments at the end of the page):
I don't know the answer to your CS6 question.
If you don't change the languages in the app descriptor xml, does it then load all languages, or just English? I'll know myself soon, an app I made is "waiting for review", and it was made with AIR 3.2, but I didn't set the languages in the xml.
About CS6, I can make an educated guess that the situation will remain the same as with CS5.5, with regard to adding newer versions of AIR, when they exist.
Not sure what happens when you leave out the <supportedLanguages>en</supportedLanguages> tag.
If you omit the tag, it might seem logical to expect that the App Store would go by the choice you made for "Default Language" iTunes Connect, prior to uploading your binary.
Unfortunately, that does not happen. Instead, omitting the tag causes all languages to be dumped into your app's description (currently English, Czech, Dutch, French, German, Italian, Japanese, Korean, Polish, Portuguese, Russian, Simplified Chinese, Spanish, Swedish, Traditional Chinese, Turkish).
Unless you are planning to support all of those languages in your app, it's probably best to specify the <supportedLanguages> tag in your application xml!
What's the real difference between listing all of the languages or only the supported ones? Your app is not listed for users of the unsupported languages? I hope not, because sometimes we get new customers which use languages still unsupported in our app, and then we add localizations for their language after subscribing to our service. Would it hurt visibility not to list all languages?