I think the Karma would have failed even without the Mavic being sold as there were just too many issues with it, if the Karma had worked well though I think the Mavic would have still been a death blow. I liked the approach GoPro took in that they didn't just try to make a copy of an existing DJI drone but instead made something that would potentially appeal to those with GoPro equipment already or would want to use a stabiliser and GoPro camera for other purposes. Preorders also received a two year accidental care warranty for free and GoPro could potentially offer much better after sales service than DJI.
Then when the first Karmas were released, they had the fault they were falling from the sky which killed off any idea of getting a Karma for me as I'd bought a GoPro3 Black Edition on the back of glowing reviews and found it to be a highly unreliable beta device that wasn't ready for release. When the Karma came back out for release here the price actually went up and they'd removed the free accidental care warranty plus the drone still seemed to be suffering issues with low batterylife, poor range, not holding its position well and the camera angle not hiding the props.
Even if the Karma worked well it was clearly an inferior drone compared to the smaller, lighter, faster and better featured Mavic leaving the GoPro to rely on its stabiliser and separate camera which didn't seem that great either. The Karma stabiliser seems difficult to mount for using on a bike, the extender kit is pricey and the battery is fixed so I decided Zhiyun gimbal was a much better choice. I was initially after a GoPro5 but bought a Xiaomi Yi 4K when I found it had much better batterylife than the GoPro and the mic works fine with a gimbal whereas the GoPro5 doesn't.
I am disappointed DJI weren't able to produce a competent rival as it's never good when one company is dominant with little competition but the Karma had way too many issues.
John