Nothing official from Apple, but Venturebeat gets a lot of info in the form of informed speculation and anonymous 'tips'.

Interesting to say the least.
I have to hand it to Apple’s own engineers. They sure know how to shut up about their work. But that leaves me looking to readers again for answers. Is Apple’s A4 really a modified ARM A9 Cortex with two CPU cores and some type of GPU core? Email if you know more than I do.

Update: A former Apple engineer writes, “A4 was stated to contain an ARM Cortex-A8, not an A9. It was an internal source that told me. I trust them. No confirmation on which SGX, but it is one.”