The 2019 iPhone models haven't even been officially announced yet, and we're already starting to see reports about what will be in the 2020 iPhones. We've compiled the most notable ones here, but take these with a big grain of salt. Even if these reports are accurate representations of what suppliers are saying, or come from moles within Apple itself, the company's plans can and do change. There's still plenty of time before the design and features have to be totally set in stone.
Update 07/22/19: Well-known Samsung leaker @UniverseIce on Twitter claims that Apple is in talks with Samsung and LG to provide a 60/120Hz switchable display for the 2020 iPhones.