Splatoon 3’s main campaign and the Side Order DLC overhauled the single player experience, so making a fully single-player spin-off makes perfect sense. Ever since Breath of the Wild Nintendo has wanted to make more of their games open world, and it may work in Splatoon’s case; they may be throwing spaghetti at the wall and try to see if sticks. Just making a Splatoon 4 and calling it a day would be too easy and predictable, it can wait.