I've been anticipating Blue Mage so much, I still don't know what the final rundown..

[Istaro]

There haven't been anything than hints about what will show up in Shadowbringers.
We don't even know for certain that there will be any new classes introduced with the Shadowbringers expansion.

Blue Mage has been announced, and that will show up in patch 4.5 - thus prior to the release of Shadowbringers.

There have been hints that there will be a new class based around the gunblade - and that is all we know for sure about that.
Speculation and unconfirmed leaks indicate that there will be one additional class, with Dancer being the most common guess.

In short - we don't know, but guesses are plentiful.

You didn't watch the keynotes at Fan Fest.

"Multiple new jobs" was part of their keynotes, Blue Mages was not counted among them. So it was confirmed we'd have multiple jobs on Shadowbringers, likely 2.