The email, posted to the Web by Owened (via The Verge), is seemingly meant for members of Nuance's NDEV Program who are using SpeechKit 1.4.5 speech services.
Technology from Nuance was recently confirmed to be part of the Siri voice-recognizing assistant, meaning the company works closely with Apple and could be privy to upcoming launch information.
There is, however, some confusion over the email's use of iOS 7 "GA," which means general availability, a term often confused with "GM," or golden master. Traditionally, Apple has released GM versions of iOS to developers alongside a new iPhone's release, with the GA rolling out a week later.
Apple is expected to announce both a next-generation "iPhone 5S" and a lower-cost "iPhone 5C" at a special event on Sept. 10.