Rumors for an ultra-high resolution Canon full-frame mirrorless camera are heating up. What began months ago as whispers that the Canon 5DS and 5DS R would be replaced by a mirrorless equivalent has turned into a new report that claims to reveal the specs of a Canon prototype that’s currently being tested. Canon Rumors received this spec list just 24 hours after Canon News unearthed a patent for an 83MP image sensor that might be at the heart of this…