The difference here is that the Wii U is not a good indicator of future success. It is mostly comprised of people who really like Nintendo versus the X1 and PS4 with have a more equal casual/dedicated fanbase. So success on the Wii U really doesn't convince me of anything. Many games also sell biggest on their first title, there is nothing to suggest that won't be the case here either. That's part of why I entered this thread, it's ridiculous to predict a series size before it even has a sequel to compare to.
Yeah, but splatoon doing this extremely well for a game on a limited userbase practically shows how scary this would do on an actual system that sells or on a HH.
If this were on 3DS as well it would most likely be over 2mil by now in japan.