While the mobile world is full of leaks, I am not inclined to believe this one until I see Apple announce it at WWDC next month. The Verge wrote up an informative article focused on developer support for such capability and while it may be possible it looks to be quite an effort that seems limited to only the larger iPad displays. Apple traditionally likes to have a consistent experience across iOS so having a function specific to just the larger display iPads doesn't seem likely. Then again, there are also rumors of a "professional" iPad with an even large display so we just might see it eventually.
Given the price of an iPad compared to a MacBook Air I would think those who want a productive mobile device with split-screen support would just get an MBA that even has a keyboard for optimal productivity. While tablets can be forced into a work mode, the experience is always a compromise at some level. Recent stats show that tablet growth is declining as people realize tablets are optimized as companion products that can't replace laptops.
I personally use the split-screen functionality on my Surface Pro regularly and find it very useful. However, Windows is designed to be a multi-tasking OS and the experience is quite refined in Windows 8.1. If Apple can implement the split-screen multitasking capability across apps, similar to what Samsung does on the Galaxy Note phones and tablets, then there could be some real value here for iPad users. I know some people who bought Samsung Android tablets because of the multi-screen support so Apple may be looking for ways to keep tablet buyers from jumping to Android.
My daughter recently received her Microsoft Surface 2 and even having split-screen support on an iPad wouldn't be enough for her to give it up. I have an iPad Mini with Retina display and have no desire to use multi-tasking on a screen of that size.