I would be very, very surprised if they were using UE3, considering their games haven't seen much of a graphical update since... 1994? Really old school in literally every single way. Think Ultima Online, then take a step back from that.

However, I wouldn't be surprised if they suffered from a similar regression.

64 bit stuff in iOS 8.3 broke the way we were using 3rd party zip libraries in my iPad project. Before that, it had been completely stable since iOS6. Am now rewriting in Swift and using Storyboard, with xcassets taking the place of zip files.

That will orphan apps who just want to deliver updates (e.g. app security, unrelated to OS) for older versions of iOS. Orphan apps will need a distribution channel that can reach older and still-useful devices.

It might be technically possible or even trivial to fix the engine, but impossible for other reasons.

They are talking of licensing a new engine. If they licensed the current one, too, it might just be a matter of a vendor that went out of business or killed the product.

Not the engine author, but from our app experience:

Tracking Apple's breakage (in minor releases, even) and fixing our code -- code that was written to the defined API -- is a cost that is rising precipitously as Apple's quality and stability keeps going down.

If you have revenue from other platforms, it can make sense to just say "f it" and drop the platform. The AppStore is a shitty retail pipeline; 30% is a crazy commission for digital software distribution, the single-retailer-monopoly + appstore design is driving prices to unsustainable levels, etc.