Take a look at this article, I had never heard this theory before but it might make sense given the long delay...
http://www.valuewalk.com/2012/06/is-apple-inc-aapl-ready-to-ditch-intel/
http://www.valuewalk.com/2012/06/is-apple-inc-aapl-ready-to-ditch-intel/
Intel still supplies Apple with all of the chips for their laptop and desktop computers. If rumours prove to be true that could be changing. Apple has not yet updated its iMac series of desktop computers. Some believe that part of the delay might have to do with the introduction of computers running on ARM processor technology much like the firms mobile devices.