Canon camera sales are mainly dropping due to these main reasons:
1) Smartphones are killing P&S market. What is Canon's response: do the same thing as every year, i.e. issue new model P&S cameras. I would think that Canon should abandon this dying P&S market and concentrate on more advanced cameras.
2) There are practically no news in advanced DSLR area and market became saturated. Canon is still milking DSLR market by manufacturing the same products and customers do not have any options even if they want to upgrade their current camera into new one. e.g. I have Canon 7D and waiting for 7D II for long time. It's a real shame to milk the same dying cow for so many years. Canon has all required money for R&D but we see only limited inventions from its side. One invention (dual pixel technology) is really not ground braking.
3) Canon is losing and will loose significant market to the third party lens manufacturers such as Sigma and Canon. We see significantly improved quality in both these firms and quite significant increase in their lens sales. Of course, Canon is still a king in fixed focal length lenses (tele), but their price is enormous and not affordable to many consumers. From other side, its is really a shame for Canon not to upgrade the most popular lenses (e.g. 50 mm., which is produced for more than 20 years). Come on, Canon, you can really do better. If the same trend continues Canon will lose very significant lenses market to competitors.
4) Lack of innovations: when I look around I here when people talk about Tamron and Sigma lenses, Sony, Fuji, Olympus mirrorless cameras, Pentax medium format cameras, etc. Canon is currently leading company with biggest profits and very significant loyal customer base (loyalty is due to expensive lenses, which were bought some time ago). If you do not introduce new and expensive technology and still produce large quantities of goods, your R&D costs are recovered long time ago. Canon is really able to reduce prices for APS-C and full frame cameras but they are still milking the same old cow
Also, I see other trends that many newspapers and mass media are laying off photographers o even suggesting to journalists to make pictures with iPhones. I see the trend that in the nearest future only serious hobbyists will buy DSLR cameras, however, number of such people is constantly decreasing.