I agree with this. While there is some incentive for Apple to artificially hold back new features and reserve them for newer devices, there is little incentive to hinder performance because it hurts their brand image.
It's embarrassing right now. I know this is an edge case, but at the iPad 3 release Apple commented "iPad is known for it's fluid graphics performance." Apple was known for speed and fluidity. The fact that Apple's still selling devices with 2011 and 2012 chipsets is bad enough. If the general consumers walks into an Apple store and buys an iPhone 5C today and iOS 9 ruins performance on it in 6 months they will have the impression "Apple sucks" and will not buy another devices. If enough consumers get burned and word of mouth spread fast enough Apple could have a huge problem.
My iPod Touch 4 maintained decent speed iOS 4 -> iOS 5 - iOS 6 (a little slow)
My iPhone 4S and iPad 3 lost no speed going from iOS 5 to iOS 6.
iOS 7 brought notice slowdowns to these devices. I think part of that was bad programing (which was partially fixed in the iOS 7.1 update) and part of it was honestly the ridiculous amount of graphics overhead that iOS 7 brought with it's translucency. I had expected iOS 8 to rectify iOS 7's issues, but they made them dramatically worse while also making iOS dramatically more powerful. iOS 8 was a big change for the better, but it was released too fast and wasn't ready. The annual iOS updates (and OS X for that matter) create the potential for major new features to not be ready yet, but released anyway because if an iPhone is released without a new iOS the world will crumble.
The current state of their software is mediocre in many ways. My iPad 3 and iPhone 4S had no lag on their native OS. My iPhone 6 stutters from time to time. There are still bugs (mostly minor) that I experience on a daily basis. My hope is that iOS 9 will not introduce major new features, but enhancements on existing ones and performance improvements. One performance issue that simply amazes me are when you open apps that I suppose have been refreshed from memory and you get a static screen of what it looked like for several seconds before it actually loads. It's much worse on my iPad 3, but happens occasionally on the iPhone 6. For example, I open the must app and it shows the album art of a song I played yesterday for about 5 seconds before it fades to my album list. Why?
Apple doesn't have to introduce "AMAZING" new features to make a great new iOS. Just enhance existing apps. For example:
- Access to the document picker in the Mail app
- Increase document picker performance (it's so slow to open)
- iCloud Drive app
- Album art view for iPad Music app like in iOS 6: right now it's a stretched out phone app
- Better app switcher for iPad:why does it show the same amount of info on a 9.7" screen than on a 3.5" or 4.7" screen?
- Display both the today tab and Notification tab at the same time when the iPad is in landscape mode in notification center.
- Allow landscape mode on iPhone 6: don't rearrange apps, just allow apps to rotate 90 degrees.
- iOS Dark Mode: I like the dark translucency of NC, lets have more of that.
- Customizable Control Center shortcuts: I never use the timer, let me change it to alarm clock. Also, I never use "Do Not Disturb," let me replace that with personal hotspot.
- Fix location based Reminders that sometimes do not alert you.
- Fix the "A problem occurred and the page was reloaded" issue in Safari. Never had this issue on any device until iOS 8.
- Remove that "Tips" app.