It's not unlike the problem Apple encountered with the iPhone 12 Pro last year, where it was forced to nix the 120Hz "ProMotion" display technology due to a shortage of driver chips. In that case, Apple was unwilling to delay its flagship iPhone release, so it simply went with the older display technology. For the 12.9-inch iPad Pro, however, there's a good chance the new display will be one of the marquee features. Further, this isn't so much a component shortage as a production delay.