MMORPG.com user PottedPlant22 has brought in an image found in Final Fantasy XIV that seems to hint at the Blue Mage and its potential for its possible inclusion at a later date. The image contains an "Ancient Eastern Proverb" that mentions crimson embers, hinting at the Red Mage, and "azure lost amidst the squall" that may indicate a Blue Mage.
Speculate away before visiting this Final Fantasy XIV forum thread here at MMORPG.com.