Canon announced the EOS-1D X camera in October 2011 but delivery did not commence until the second half of 2012. I bought one of the earliest production models and have made it my main wildlife camera body since. My readers know I have picked this to be the best full frame DSLR for wildlife and sports photography. The camera received a major firmware upgrade in January 2014. When the action is a bit further away, I use the EOS-1D Mk IV and the EOS-7D Mk II, since I am not a big fan of extenders.
As a wildlife photographer using Canon equipment for 25 years and the EOS-1D series since 1989, I have followed the line with keen interest for many years. My biggest 'complaint' about the camera is the 18MP sensor does not offer enough pixels when it comes time to crop the photos. Canon plans to introduce the EOS-1D X Mk II some time late 2015 or early 2016.
Pre-production models are already in limited circulation among photographers who signed non-disclosure agreements. The Mk II camera will employ a new, higher pixel sensor, perhaps in the low 20MP with an unparalleled AF system and improved ergonomics. Rumored to be slighter larger in size but perhaps maintaining roughly the same weight due to improvement in material and a new battery. The main processor should be the dual DIGIC 6+ with an additional processor for an advanced metering system. Keep checking back for the latest information as I receive them.