8K Video exists and it plays at 7680×4320 on youtube

8K resolution or 8K UHD is the current highest ultra high definition television (UHDTV) resolution in digital television and digital cinematography.
TV manufacturers pushed to make 4K a new standard by 2017.

Patagonia 8K explores the beautiful and rough landscapes of southern Chile and Argentina. Shot in 8K resolution on a medium format camera it's aimed to deliver the most realistic experience.
Shot in 6 weeks, travelling over 7500km from Santiago to Punta Arenas we captured roughly 100.000 still frames that combine into this timelapse video.

GEAR LIST:
-Pentax 645Z
-Pentax 25mm f4
-Pentax 55mm f2.8
-Pentax 120mm f4 macro
-Canon EOS 6D
-Canon 70-200mm f4 L
-Canon 24-105mm f4 L
-Samyang 14mm f2.8
-Sony A7s [metabones adaptor]
-eMotimo TB3 Black
-Dynamic Perception Stage One [with customized carbon rods]