Apple currently is making iPhone X, but displays for this phone will be produced by Samsung because Apple isn't able to produce as many screens as Samsung, and firms reached an agreement in this topic. Similar agreement probably will be reached in the nearest future between LG and Apple, because Apple has big plans for new foldable iPhone.
Deal still hasn't been completed, but it's very close and Apple will invest around 2,6 billion $ in LG's support in topic of displays. We don't have any concrete dates about possible presentation of foldable display by LG, but over two years ago LG presented prototype of this screen and since this moment company haven't mentioned this topic. If it comes to Apple's foldable device, probable date of its premiere is 2020.