The unveiling of a new iOS doesn't just give us a look at the software we'll be using on our iPhone and iPads over the coming year, but it's also a bellwether that offers us a chance to see how the company is responding to the pressures it is facing.
Two things separate the iPad Air 2 from the earlier iPads. The first of those differences is that the iPad Air 2 is the first iPad to feature 2GB of RAM (it's predecessor had 1GB). The other difference is that it is the first iPad to feature a triple-core processor, giving it more horsepower.
Whatever the reason, if you want to use two apps simultaneously, the price of entry is a new iPad Air 2.
So while Apple will push iOS 9 out to everyone running iOS 8, thus keeping fragmentation low (a metric which is important to developers, analysts, and pundits), not everyone getting iOS 9 will benefit from all of its features. I'm pretty sure that Apple will feature Split View in iPad ads, to make sure that those running old hardware know what they are missing out on.
It's nothing new for Apple to give users access to a new OS release but prevent them from using all the features if they are running the release on older hardware. This time Apple is hoping that those who don't own the latest and greatest iPad will feel like they're getting an iOS 9-lite experience and will part with a few hundred bucks for a new tablet.
Sales data for the next few quarters will let us know whether this was successful in jumpstarting iPad sales.