Technically it would be possible if the new job is a different instance of Blue Mage.

Thematically, it could make some sense, if we do find the original Whalaqee Blue Mages and learn from there. But that could be a really distinct aesthetic approach, because the whole mask iconography, monikers and dandy outfit are all a Celestium fabrication to make Martyn and the WoL more 'marketable'. It seems that the only aesthetic thing that a potential 'New World BLU' has in common with the 'Celestium BLU' is the relevance of the color.

Still, very unlikely imo. But not gonna lie, it would be really weird to wait 3+ years for an update that would bring the job into the New World... Unless they decide that the Whalaqee lands are in a completely distinct area that is not yet accessible in Dawntrail (north maybe?).