According to the game’s Wii U eShop listing, Splatoon may support Amiibo.
The eShop listing tags the game into several different “Related Software” categories, including “Nintendo”, “Action”, and “Multiplayer”; it also tags Splatoon in the “Amiibo” category with games that support Amiibo figures. This suggests that the game will support the figures in some way, and further supports the alleged Splatoon Amiibo rumor. However, it could be the case that the game will support existing Amiibo, similar to Hyrule Warriors and several other games.
— Dakota (@Dakotam4711) March 10, 2015