Apple is said to be planning to release its iPhone 6 later this year with the announcement scheduled for September 16th and the phone will be released on October 14th. It is said that Apple will have a very busy October, so maybe we will see the rumored iWatch at the event as well but nothing concrete has been stated so far.
The source is said the be a senior Apple Store leader but it is worth pointing out that the date does not align to previous releases; Apple typically releases new iPhones on a Friday but the 14th is a Tuesday. The reason for this is that Apple expects significant demand and believes that it will have enough inventory to meet initial demands thanks to a massive upfront order.
It's still up in the air if Apple will release a 4.7in and 5.5in iPhone later this year or if the 5.5in device will arrive at a later point, if ever.
The timeline certainly seems plausible as Apple has previously released iPhones with a similar timeframe to make sure that they have new devices out before the holiday shopping season.