Canon is losing quite a few landscape photographers these days, because there is stiff competition to fill all the broad and niche landscape needs. I still use Canon for landscapes because I like their system and I have no complaints with my process. I can still see vast majorities of people wanting to get into landscapes who are not even considering Canon because of lower MP and less DR. I personally stitch and bracket all of my shots (never missed a shot), so I have not much to gain by leaving Canon, but others certainly see the need.
Respectfully disagree, Johan. Canon isn't really losing folks to mirrorless nearly as much as they are losing folks to Sony sensors -- people are 'switching to mirrorless' just to get their hands on what they think will get them better IQ.
Consider: one of the Sony a7 bodies with an adaptor is probably the cheapest way to get a "better" sensor for FF work without having to flip all your glass. Landscapers are the ones willing to give this a try first, as they need AF far less than most photographers and LV can get them by.
But we continue to hear of everyone leaving Canon for a host of reasons, principally due to the sensors, and secondarily due to their avoiding any significant commitment to mirrorless.
Canon will eventually commit large dollars to mirrorless and make a proper go of it -- with APS-C, not FF. (I don't see a 4th mount happening. But they'll pony up an EVF, offer DPAF, and (please) offer a greater variety of small, native EF-M lenses and people will buy it.
The big wild card is when. I've heard a thousand forum-dwelling photography enthusiasts that claim that Canon is falling so far behind and that everyone is leaving them, but I haven't seen a speck of sales data that shows that Sony / Fuji / etc. are converting large numbers of DSLR users from them. If that starts to happen, Canon will deploy more competitive products in that segment.