I did something a few days ago that I've never done before. A friend of mine expressed an interest into getting a DSLR. He wants full frame. Before, I would have naturally suggested he get a Canon, or at least leaned in that direction. In fact he asked what Canon I suggest he get for his needs.
I discussed the current Canon options with him, but I also suggested he take a look at the Sony offerings, and possibly even Nikon as well since he doesn't have an investment in glass at this point. We will see where he ends up, and certainly he wouldn't be well versed on things like dynamic range, etc. at this point but it wouldn't hurt to look at the competition before he blindly goes to Canon.
From a digital standpoint, I've never owned anything but the 5D series of bodies (unless you count the M3). For me the 5DIV was a welcome upgrade from the Mk II. While I don't shoot the 6D series, I'm confused as to why they would not upgrade to their newer sensor technology. I read somewhere the speculation that Canon wanted to make use of the older production lines which may be the case but I'm not quite sold on that concept yet. The more likely reason in my opinion is to keep it a level lower than the 5D series and provide potential new FF shooters and upgrade path for the future. That is all well and good, but you also open the options to the competition when they are offering as good or in some cases better performance for the same money.
I wouldn't jump ship at this point unless something truly drastic went wrong with Canon, but if I were just getting into photography and wanted a DSLR FF, I suspect I would be looking at other products before pulling the trigger. Personally, I'm waiting to see what happens with the 5DS Mk II, since I was very close to getting that instead of the Mk IV. If they continue the improvement with dynamic range, and at the higher resolutions of 50+MP I could make a case for having both in the stable. I'm really curious as to what they do with Foveon technology if anything.