Most likely they'll adjust the Job to be linked to a Class and then when you become that Job the skills you obtain via Job Quests will have you fight certain instance bosses to obtain their strongest skills similar to how Summoner had to fight the Egi before he or she can summon the Egi.

In short the only aspect of a Blue Mage in FF14ARR will be just it's Job skills while all class skills are just basic normal class skills not related to Blue Mage.