According to BGR, carriers are indeed testing new nano-SIM cards in partnership with Apple. The news comes shortly after a report earlier this week claiming that European carriers were stockpiling the new nano-SIM cards in expectation that Apple will begin to use the smaller card in the next-generation iPhone.
According to BGR:
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.
Regardless of what speculation points towards, we’ll find out soon enough when Apple announces the next-generation iPhone or something more definitive is leaked.