Are they saying a choice of Nikon or Canon mount, or it might be one, it might be the other? There would need to be a lot of upside to it for me to want to add it to a stable of Nikons. I suspect the primary buyer would be someone heavily invested in Sigma glass that's tired of having to send it back for firmware upgrades every time Nikon/Canon issues a new body. That's me, in a way, but I'd need to see a year or two of field reports or get one in my hands on trial for a couple months before I bought.
The issue for them is going to be finding the sweet spot in form and function that temps the user of the other brands. If history holds they'll err on the side of the Canon user.