Canon is often accused of being too slow to react and update their line compared to the competition. However when you look back and see cameras like the 7D Mark 1 which introduced 60p 720p video to the EOS line it is much harder to judge them as other cameras topped at 30p.
The 5D Mark III has been a best selling camera for Canon but it is getting long in the tooth. The lack of 4k video is a sore spot for the camera line that introduced cinematic looking footage to the masses. The upcoming 5D mark IV (4) rumors suggest that not only 4k is in the cards but 1080p 120fps as well.