TSMC started sampling the A14 Bionic SoCs earlier than usual, as a recent Chinese report claims Apple already received the first engineering samples in late September. Apparently, there is also a downside to making the jump from 7 nm to 5 nm: the net die per wafer ratio gets reduced and 2020 iPhone prices could end up being even higher than the current gen.
https://www.notebookcheck.net/TSMC-already-sampling-Apple-s-5-nm-A14-Bionic-SoCs-for-2020-iPhones.440058.0.html