Preview at WWDC likely in June, followed by September launch.
Carriers Reportedly Testing Nano-SIMs for Apple Ahead of Next-Generation iPhone Launch
Multiple carrier sources have exclusively told BGR that Apple is supplying nano-SIM adapters so its carrier partners can test how nano-SIMs work on their networks in standard test devices before they are widely deployed when the new iPhone is introduced. This includes AT&T.
SIM card form factors with nano-SIM at left (Source: Giesecke & Devrient)
As we noted in the our report earlier this week, a part leak back in early May suggested that Apple would continue to use micro-SIMs in the next-generation iPhone, but with the new nano-SIM standard backed by Apple having been approved last month the company may already be pushing forward to adopt it as a space-saving measure.