Apple Analyst Ming-Chi Kuo believes that the 2019 iPhones and upcoming iPad Pros will have better wireless performance, thanks to new antenna material.
Instead of LCP, or Liquid Crystal Polymer (the ones that are on the iPhone XR, XS Max, and the XS), Apple may choose MPI, or Modified PI as it offers better RF performance for their future iPhones. The MacRumors representative has made mention that iPad models may continue using LCP as the primary 5G material for the iPhones that will be released starting Q4 of 2019.
On a separate note, Kuo has mentioned that new iPad Pros for both the 11 and 12.9-inch variants are set to enter mass production between Q4 2019 and Q1 2020. These models are said to have flexible boards made of LCP material, but for more details and specifications we’ll just have to wait for the English research notes.