For me, the biggest debunk to the Spirit debate is the fact that Spirits were determined before the DLC was. This suggests that Sakurai himself either placed Geno in low priority (which given the newcomers we ended up with is VERY possible) and/or securing the rights to Geno was originally more laborious than Sakurai was willing to pursue. That said, if corporate Nintendo was behind the DLC picks, and they gave us Banjo-Kazooie, it's entirely possible that a greater focus on fan demand was taken into account rather than solely Sakurai's whimsy, which would make sense when you want the maximum amount of people to buy something. Regardless, the afterthought nature of the DLC, or possibly future DLC, means that literally anything is possible for inclusion, with the only concrete exception being assist trophies.
In short, the balance between 0% possibility and 100% possibility is 50%. We don't have enough data to conclude one way or the other based on a JPEG that was decided on 2+ years ago.