As other leading smartphone makers are perfecting devices with vertically or horizontally folding screens, recently published patent information suggests Cupertino might take a different route. A patent for “electronic devices with rollable displays” filed last October and published on July 13 references a device with a display that could be moved between an unrolled state where it is planar and a rolled state for storage.
I can imagine some use cases but they would be in addition to your phone not a replacement. Like a smart band sized device that can be pulled out into a usable display. But afaik were years away from that being possible. A device like that would be good for when you’re exercising or whatever, assuming it could be made moisture resistant at least.