I suspect a modern 45 MP sensor with DPAF and possibly IBIS based multisampling will compare very favorably with the 5DSR. Then, after Canon sells a bunch of those, they can bring out the enhanced high MP version. Canon knows how to sell cameras.
Edit. Before Digic X it didn’t seem like the processing was there for a high speed camera hence the acceptance of the slow FR high MP rumor. Canon might have been doing their homework.
the 5Div is still a fantastic camera, I have owned all the 5Dline cameras to date, for me the only problem I have is the miss rate of using a 35ii 1.4 and 85L1.4 on it as it uses PDAF, I find the new way of autofocusing on the mirrorless to be quite and advantage and thats what drives me to get one, I'm just wiating as the current R is not much of an upgrade. But we know things are happening soon with new releases so its a bit frustrating but good times ahead I believe.