The High Yield YouTube channel has a good early look at die shots of the new A20 chip used in the iPhone Duo and discussion of the changes from the prior generations.

https://www.youtube.com/watch?v=t8bxkCKNiuA

They have a similar video comparing the M6 to the M5.

https://m.youtube.com/watch?v=uA7WLmlg1kM