I wonder if sales may be slow due to plain uncertainty about what's happening with other products...we all suspect a 5D4 to be announced "soon", but I think a lot of people are sitting on the fence until we see what that camera's specs are, to say nothing of a 6D2 although I suspect we will wait quite a bit to hear on the latter.
I think a lot of people are hoping the 5d4 sits somewhere between the 5d3 and D800 in terms of resolution with some significant improvement in DR to close that gap. If it does, I predict it will sell very well, even to landscapers like me, and the 5DS will end up being a niche body.
As a landscape shooter, that's what I would like. If the 5d4 turns out to be a low MP, low light camera (that a lot of people also understandably want), then I will likely buy a 5DSR since it appears to be a step up (at least for what I do) from the 5D3 and I do want at least 24MP of resolution in a new body. So I am waiting.
I really hope Canon makes its plans clear pretty soon; I think a lot of people want to upgrade their 5d3's but don't need/want what is basically a very high MP version of it. I suspect quite a few of those customers may just end up trying the A72 or A7R2 due to not knowing what/when Canon will do, even though they really would prefer to stick with Canon.
Waiting to announce plans may sell a few more 5d3's, but it could also sell some A7's.....
