Apple plan their devices many years in advance, but plans can change based on technology innovation, and supply line issues. Personally I believe that Apple wanted an OLED display for a forthcoming tablet and put the tender out to Samsung (and maybe LG). Samsung then came back with a display proposal using the single stack OLED but for whatever reason, Apple wanted the tandem stack (better lifetime, higher brightness) but could reach agreement with Samsung on pricing, thus Apple walked away. Who knows, perhaps Samsung will suddenly capitulate and meet the price point Apple is demanding and the OLED iPad is back on.
I was worried about OLED burn-in on largely static displays such as laptops and tablets, but they have been out long enough now to see that that isn't such a concern (probably due to pixel shifting and voltage adjustment) so the only thing lacking is brightness compared to LCD. The miniLED iPad can hit 1600 nits for small portions of the screen and 1000 nits full screen brightness. I have no doubt that an OLED could hit 1000 nits for highlights (the iPhone 13 Pro hits 1200 nits peak), but would struggle for full screen brightness - I would much rather have the per pixel control and lack of blooming of OLED compared to any LCD technology.