I really don't think it will. FF fanbase is so damn loyal to the games, even if their quality (IMO) has significantly declined post-ps1 era. Based on the recent history of the series, I am way too skeptical of FF15, but it seems people are still holding out and have hope, thus I think it will probably outsell Splatoon.
Still, I'm really surprised with the performance of Splatoon. It's deserved, though. Game is super fun.
Hi