The best barometer for these is probably the X/Y 3DS XLs. I'd expect these to be in generous supply initially but it's hard to say if they'll be easy to find on Black Friday. My guess is that any place where these are available at a lower rate on BF will sell out any left over stock within the first hour or two of BF/ Thanksgiving night.
Once BF has passed, I would also expect these to become much harder to find and I doubt Nintendo will add much more stock after the initial release. I may be wrong, but I don't think the pokemon x/y systems were ever restocked. They just happened to be far more plentiful initially.