iPhone 6 with the 5,5 inch display can be delayed. Apple is not satisfied with the batteries for a large iPhone 6, which currently offer manufacturers. The fact that the standard thickness of batteries of 2.8-2.9 mm, but for iPhone Air need to reduce this parameter to 2 mm. Now this task is unsolvable.
Expected that the problem will be solved only next year.
But iPhone with 4,7 inch display can be released on time.
If you want to know about release date continue to follow the news.