It has been reported that TSMC could have a 5 nm FinFET process ready for commercial use by 2020, and the rumored Apple A14 SoC would be one of the first chips to benefit from the advanced technology. The semiconductor foundry has announced it will start risk production for 5 nm technology in the second half of this year.
https://www.notebookcheck.net/Apple-A14-SoCs-based-on-TSMC-s-5-nm-process-could-feature-in-iPhones-by-2020.410689.0.html