With NPD DisplaySearch, the first one to volunteer a time frame for the 2,048×1,536 resolution 7.9-inch display, the scheduled production was to start in July. Still an achievable target for NPD, the others are likely to push the production target back.
There are a lot of factors to be considered before its production as the Mini is very thin and requires something 3 million pixels.
The Low-temperature polysilicon or LPT used in the 4-inch display on the iPhone 5 seem to be impractical for larger 7.9-inch screen of the Mini. That concludes with, the larger the screen, the lower the production yields. Manufacturer: Japan Display Inc. (JPI).
Amorphous has been widely used in the iPad 3 and iPad 4 and may not be suitable for the thinner display of Mini Retina. Manufacturer: LG Display and others. Furthermore, IHS iSuppli has confirmed that high volume production of the display would suffer until the fourth quarter.
As a matter of fact, Apple is continuously pushing the margins of hardware tech. And some technologies do take longer time.