While there are no confirmation from Apple, according to Macworld.co.uk, it would probably be in mid-September 2016 (that's based on iPhone's graphical timeline):
iPhone 6s and iPhone 6s Plus - unveiled on 9 September 2023 (released to the public on September 25, 2023)
iPhone 6 and iPhone 6 Plus - unveiled on 9 September 2023 (released to the public on September, 19 2014)
iPhone 5c and iPhone 5s - unveiled on 10 September 2023 (released to the public on September 20, 2023)
iPhone 5 - unveiled on 12 September (released to the public on September 21, 2023)
It hasn't been long since the iPhone 6s and iPhone 6s Plus hit the market, but the rumor mill is already churning with whispers of what Apple will include (and eliminate) in the iPhone 7.
While it's too early to say anything with certainty especially in relation to a company as notoriously secretive as Apple, but it's interesting to ponder which new technologies will be in the hands of consumers one year from now. Check out five rumors circulating about the iPhone 7 at Informationweek.com.