A new report from The Elec suggests that Apple will introduce iPad Pro and MacBook Pro models with double-stack OLED displays that have two layers of the light-emitting diodes and thus achieving double the brightness. This seems to be in line with an earlier rumor from September. The current issue is that the tech is expensive and the manufacturing process is not fully developed so the sources familiar with the matter say the first units won't arrive until 2023 or 2024. We do know, however, that the price of the panels would allow Apple to use those only on the 11-inch and 12.9-inch...
Source: https://www.gsmarena.com/apple_ipad_pro_and_macbook_pro_to_use_new_oled_tech_allowing_higher_brightness-news-51690.php