I think there are some market share losses, but in my experience, I still see way more Canon than anything else. I shoot at a lot of press events for big companies and a lot of trade shows, and Canon easily accounts for two-thirds, if not closer to three-quarters, of the cameras I see overall. It varies by event, of course, but out of dozens in the last couple years, I can't recall any event in which Canons weren't at least half the field.
What's very interesting to me is this-- the video scene at these events is still dominated by Canon. I've noticed a few internal PR teams have switched to Nikon gear, and last year at CES, Black Magic cameras had a small but noticeable presence. As someone who will be fairly outraged if the 5D Mark IV (or some other 2015 $2000 - $4000 Canon DSLR) doesn't have a great 1080p implementation and a decent internal 4K implementation, I find Canon's resilience in this market interesting. I used to see more Sonys (e.g. FS100s) among the people who weren't using Canon DSLRs for video; now, I see more C100 and C300 bodies in this group. That said, most of the Canon bodies I see are at least a few years old-- i.e. lots of 5D Mark IIIs, some C100s, even a few t3is and 60Ds. Not seeing any 70Ds yet and it's still too early to have expected a 7D Mark II sighting-- but the reason I bring up the prevalence of older models is this: When I do see photo/video combos that aren't Canon, they're usually micro four thirds, not Sony. This is all anecdotal, of course-- but since we're talking about demographics in which Canon is retaining users, I thought I'd add another set of observations.