As I said, there are so far only rumors, which we hear from Asia, so we should first panicked. However, it is not the first time that we hear of any complications or delays in production. Finally, the anniversary iPhone is clearly different from the previous handsets and more changes necessarily impose higher demands on the production and thus a higher risk.
According to the Economic Daily News (via DigiTimes), there are production difficulties with the new 3D sensor and the lamination process of the OLED display, which could push the date for the sales start backwards. Logically, that is not confirmed at this time by any company – neither by the producing, even more so by Apple.
We still want to keep it in the back of the head, however, that iPhone 8 buyers may have to wait a little longer than those who want to purchase the regular new models. It really is a few more months. Time enough to think about whether Apple might consider a later event to present the iPhone 8, or whether, despite displacement, all three handsets will be announced in September.