The Nintendo install base is very different than it was during the Gamecube era. I would argue that it's even more child oriented now than it was before. Most "serious" gamers have moved on to either Sony or Microsoft and have left Nintendo behind. This means that although the Gamecube version sold well, odds are against a Wii U version selling well today, especially when only the most popular of Nintendo first party games break a million on their consoles anymore. The odds dip even further when you consider that the game is going multiplat, which would pull away anybody that bothered with the Gamecube version because it was only on the Gamecube (like my brother, for example).
That paints a bad picture when considering putting the resources towards porting to the Wii U. You can't really blame a developer for choosing to put the resources elsewhere rather than taking the risk.
You make a couple good points, but i doubt any version of this game is going to break that number, it's a collective profit they're looking for, and even then it's a port with assets ran through a filter at best.











