Leaker Ice Universe claims that TSMC is manufacturing A12 prototypes using the new 7 nm process, and the performance gains over the current A11 are considerable, sitting at ~30%. However, the power consumption is not on par with what 7 nm chips should yield, and this could be caused by the lacking lithography. The A12 SoCs should be launched next year wit the tri-cam smartphones.
https://www.notebookcheck.net/Leak-claims-Apple-s-upcoming-A12-smartphone-SoC-is-30-faster-than-A11.302884.0.html