Umm... as far as I'm aware, this female Link is purely a concept and doesn't indicate that female Link is playable in Hyrule Warriors. At the very least this proves that Nintendo gave the idea of putting female Link in Hyrule Warriors some thought.
Having said that, whether we will be able to play as female Link is still possible. Due to the nature of the story and how different characters come together, the idea of a female Link isn't weird. I don't really care much about female Link to be honest but if she does make it in the game I would understand, but at this point, accepting concept art as confirmation for a playable character is pretty farfetched.