I also believe that Apple changed 60Hz to 120Hz screen because of multitasking in mind.
Huh? That doesn't compute.
Here's one review that supports my conclusions:
A couple things to point out about the statement from the article:
1) The assumption that the 30% was from the third core turns out to be wrong. It's 30% faster in single core, and has a third core on top of that. That's a pretty good boost, especially for multitasking. Less so for most apps that are single-threaded though. There's pretty much zero way that the A9X will have more longevity than the A10X on the CPU front.
2) Upping the screen refresh rate isn't quite the same thing as adding a ton of pixels. Increasing resolution increases the demands you must meet in order to hit a certain performance target. So if I want to go from standard to retina displays, the GPU now needs to blit 4x the pixels, and the CPU has to draw into texture buffers that are 4x as big for the GPU to blit. And this demand can't really be ignored, so it increases the hardware requirements of your apps. Not by 300%, but considerably.
Upping the screen refresh rate doesn't increase the demands placed on apps. Instead it raises the ceiling of where the cap is. If you want to reach for the new cap, you may need more resources, but it isn't 2x as much. The GPU needs to blit 2x the pixels, but the CPU is drawing the same amount of pixels into texture buffers, and doing it as frequently. Think about scrolling. The time it takes to scroll from top to bottom of a page is the same, so new content is introduced at the same rate with 60fps or 120fps drawing. So anything rendering at 60fps today, will render at a higher frame rate,
up to 120fps. Anything not rendering at 60fps today will still render faster on the new iPad Pro. 120Hz is not placing any new demands, so is not "consuming" the speed boost of the CPU, but rather, giving the speed boost of the CPU something to actually do in apps like Things, Safari, Mail, etc where they aren't exactly CPU-bound apps to begin with.
So no matter what, an existing app will be smoother on the new iPad Pro than on the old one. Will all apps hit 120fps? No. But will any apps get worse on the new iPad Pro? No.