Right now, we cannot know. Pokemaster may edit Fennekin and its evo's page whenever we can know it. The time for somebody finish the game and then post it somewhere, so that Pokemaster can check and approve it on the fabulous Pokemondb.net.
But if you want my opinion, I believe that Fennekin will be different and will have a 87.5 % ratio of being a female Pokemon, 12.5 % to be a male. This is most likely because Braixen itself looks like a female Pokemon.
Read this (Funny):
In order to understand why could Braixen be a Female Pokemon. This implies Fennekin and Delphox to be, no ?