I don't think it has much to do with planned obsolescence, but I think Apple maybe should have skipped the 9.7" iPad Pro and just released the 10.5" Pro when it was ready. At the time of launch, the 9.7" iPad Pro had 2 GB of RAM and the same screen dimensions as the Air 2. The speakers and processor and all that were all still fantastic, but that 2 GB of RAM was going to age it pretty quickly, and that was frustrating for people (like me) who bought one on day one only to have it discontinued in the next iteration of Pros.
I will admit, the 4 GB of RAM and screen size difference were the two major factors that encouraged me to upgrade. Luckily the 9.7" to 10.5" upgrade felt like a HUGE upgrade to me, so I wasn't frustrated for long. The 10.5" iPad Pro is fantastic and I'm very glad I bought one. But yes, that 2 GB of RAM in the 9.7" is going to limit you in some regards with the multitasking and some of the higher powered apps.