http://thefusejoplin.com/2014/06/gopro-hero-4-vs-hero-3-plus-specs-features-and-price-comparison/

New Chip in GoPro Hero 4

The GoPro Hero 3+ packs in quite a punch with the Ambarella A7 chip. However, it
is expected that the new GoPro Hero 4 should push the limits much more with the
new Ambarella A0 SoC chip. If it makes use of this new chip, it is likely that
there will be a lot of important upgrades to the camera.

http://www.amongtech.com/new-gopro-hero-4-can-record-4k-1080p-120-fps/