Marketing to the rescue.
No one anywhere is getting an octacore.
The Sammy chip is a dual quadcore, not an octacore.
There is a world of difference.
One quad is A-15 architecture, the other is a slow A-7, designed to save power. They won't be tricked into running at the same time, it'll be one or the other.
Initial reports of the One with the Snapdragon 600 give it high marks for battery life and very high marks for speed via benchmarks and feeling of no-lag fluidity.
Would therefore expect the same of the SGS4 with the Snapdragon 600.
The design goal of the new dual quadcore Exynos is for the same high performance and longer battery life. On paper, it could work well, but we won't know until it gets used and reported.
Won't matter to us if we can't get it, that will be academic.
Lots of people probably won't be ok with not getting an octacore, and like the same non-difference of the slower quad vs. faster dual core in the SGS3, it'll take a just a little while for the general population to settle down about it, in my opinion.