Well it sort of depends.

I think anyone that's actually been labeled a 'blue mage' was a mage.

Kimari and Quina (or w/e his name was from IX) had the blue mage MECHANIC of of learning enemy abilities. But were they ever called blue mages? I think you'd be hard pressed to take either approach, a lance wielding melee dps or tank or whatever Quina was, and spinning them into a blue mage job. I think you'd be hard pressed to use them for inspiration.

While every job goes through changes in gameplay I think they'll want to stick to the 'blue mage' aesthetic. Whether that means being a casting dps, a tank, a melee support dps, or w/e, I'd honestly be surprirsed if they strayed too far.