Well known leaker and VentureBeat reporter Evan Blass has said in a tweet that the next iPhone will be released the week of September 12, 2016.
Traditionally, Apple releases their hardware on Fridays, which would mean the iPhone 7 will be released on Friday, September 16, 2016.
Of course, this should be taken with a grain of salt. While Blass has a pretty good track record, he’s been wrong on some occasions. With that said, we shouldn’t make any assumptions until Apple officially notes the dates. Typically, we see Apple announce the date in late August so we still have some time to spare.
It’s very tough to pinpoint certain dates, however. Especially with last years two week gap between announcement day and release day.