IHS posted an interesting article which details a new backplane technology that Apple is developing. So-called Low-Temperature Polycrystalline Oxide (LTPO) combines both LTPS TFTs and Oxide TFTs (IGZO, Indium Gallium Zinc Oxide). LTPO is applicable for both OLED and LCD displays.
In LTPO, the switching circuits are using LTPS while the driving TFTs will use IGZO materials. This could lead to a power saving of around 5-15% compared to the currently-used LTPS backplanes. The main drawback of LTPO, however, is that the IGZO TFTs are larger and so the display density may be compromised. IHS says that Apple may introduce this into future iPhones - but it also says that LTPO will be limited to low-density displays at first which is a bit confusing.
Apple started patenting its LTPO technology and the process to produce it back in 2014 and has filed three main patents.