Sounds like IMG has some fundamemtal IP that nVidia and AMD already license? They certainly have tied up their Tile-Based Deferred Rendering method, which never sounded that efficient to me (yet, Apple beats others graphically, so I probably don't appreciate it - maybe to do with cache efficiency?).
Apple, having understood this technique very well, might have thought of something even better.
They certainly would have to be pretty sure about their tech before sending this notification. Let's hope this... betrayal doesn't have the same fallout for customers as ~~google~~ maps did.