So... that spiderman shirt... (new job tease)

[Reynhart]

RDM was hinted at thru Ilbred.

There is a very big shortcut there. Ilberd used a kind of magic sword, a spell that is iconic for the Sorcerer/Mystic Knight/Spellblade/Magic Fencer/whatever-name-they-decide-to-give.
But, in FFXI (and only in FFXI), magic swords were given to Red Mage, so people immediately considered that ability a core part of that job, and thus, concluded that Ilberd was hinting at Red Mage.

In the end, yes, we got Red Mage, but it doesn't appear to have anything to do with en-spells.