Just found this info, not sure how old or accurate it is but thought id share. Was just on the verge of buying a 3 but as im not really jumping at the mo , probably :-) )
With a rumored release date of March 2015, here are some details that gadget geeks and sports camera enthusiasts need to know before purchasing the GoPro Hero 4 camera.
Appearance-wise, the Hero 4 will be released as a compact, lightweight but rugged action camera weighning less than 100 grams. It also comes with a special attachment fitting on anything in motion, including bikes, ski poles, cars, surfboards, kite boards, long boards, BMXs, or even helmets used in moving sports. It can be mounted on to any type of pole with a diameter ranging between 10 and 23 centimeters.
If the GoPro Hero 3 was installed with an A7, the Hero 4 allegedly has an A9 chip installed in it. This simply means that the new version of the action camera will have the ability to record 4K videos at an astounding rate of 30 frames per second. There is currently no other type of camcorder available in the market that can do this. Also, the A9 has the capacity of recording footages of 1080p at the fast rate of 120 frames per second as well as footages of 720p at the rate of 240 frames per second. This type of recording is said to end with an amazingly smooth slow motion recording because of the high frame rates.
These specs just showed that the new Hero 4 is the ideal portable camera available for capturing under water recordings as well as other extreme sports and other similar situations.
In addition, the Hero 4 will be released with a 13-megapixel photosensor as well as a new set of lenses for shooting in low-light conditions. It also includes multi-exposure capability as well as HDR WDR tone mapping, electronic image stabilization capabilities, and an improved MCTF. It features dual sensor interfaces 12-lane SLVDS/HiSPiTM/subLVDS and a 4-lane, user-friendly remote viewfinder playback. YeHaaaaaaaaaaa