Apple has blocked ad blocker Apps that work outside of Safari, this has always been in the App Store terms for developers as Apple has always recognised advertising as being one of the main revenue streams for App Developers.
The review process on ad blocking apps seems to have changed recently with several ad blocking apps updates being blocked by Apple. This relates to 4.2 of the App Store Developer Guidelines:
“Your app should include features, content, and UI that elevate it beyond a repackaged website. If your app is not particularly useful, unique, or “app-like,” it doesn’t belong on the App Store. If your App doesn’t provide some sort of lasting entertainment value, or is just plain creepy, it may not be accepted.” https://developer.apple.com/app-store/review/guidelines/
The popular AdBlock app has started to receive some rather negative reviews recently with customers frustrated that ads are not always being blocked. However some users are recognising the fact that this is not the app developers fault as Apple has recently changed it’s enforcing of the App Store guidelines. https://itunes.apple.com/gb/app/adblock/id691121579
While this is annoying if you use an ad blocker you should have some sympathy with the App Developers you’re using their hard work for free and then saying “you don’t deserve to make a revenue from it” by installing an Ad Blocker.
Personally I think the best solution is to pay for any day to day apps you use which normally removes any advertising.
It’s not all bad news if Ads popping up really pushes your buttons , Apple is still allowing ads to be blocked when surfing the web via Safari Content Blockers however these are not VPN based so only work in Safari utilising the Safari Content Blocker
Your existing ad blocker apps will not be removed you just won’t be able to update them, also don’t expect any new ad blocker apps to fill the void as they will no longer be allowed.
Looking to the future I do not think it is unreasonable for App developers to expect to make revenue through Advertising or users paying for the Apps including paid upgrades on free Apps.
It will still be possible to use a VPN based ad blocking service by manually configuring a VPN connection in the iPhone or iPad settings this will however be less straight forward than simply visiting the App store and installing an App.