Similar to how we had hints at Astrologian in 2.0, and aside from the 18th floor event, what do you speculate that the third class will be beyond potentially samurai (dps?) and red mage (healer/support?)
Personally, I think we'll have a Beastmaster class - and let me share some speculation as to why...
Egi Glamours
Summoners have wanted egi-glamours forever. The official reply has always been "we're working on it", but knowing YoshiP, it's going to be something more than we anticipated. I don't imagine it's that difficult or time consuming to bring back something summoners have always had (carbuncle) so I'm thinking that they're doing considerable work on the pet AI to pave the way for not just egi-glamours, but also potentially fairy glamours, turret glamours, puppet master, necromancer or beastmaster.
Existing Beastmasters
Just as there were Astrologians in 2.0 (though not playable), there are Beastmasters in 3.0 (Hullbreaker Hard).
Beautiful Models
Compare the gorgeousness of that tiger model with, say, the rabid poodle on steroids that is the paladin mount. It's just so stunning compared to many of the other enemies in the game. Of course it may just turn into a cash shop mount, but how great would it be to be able to summon one to fight by your side?
Tank armor design contest
The tank armor winners had some great designs, and even though it didn't win, there was one there that was very tribal-looking. Just as some of the runner-up hairstyles are in the game now, I imagine we'll get this one eventually.
Evening out the armor types
As far as I know (and correct me if I'm wrong), we have only one class each that can equip "Maiming" gear (DRG), "Striking" gear (MNK) and Scouting gear (NIN). Doesn't really seem balanced to have so much competition for things like healing and fending gear, and less for these types. Most likely we'll have samurai as maiming, beastmaster as scouting, red or blue mage as casting, and then eventually something under striking -- dancer perhaps? Since it's almost a given that we're going to Ala Migo, they probably have something else there beyond monk.
They've talked a lot about balance not just in terms of play and the amount of actions used, but also in terms of character roles.
Just my theories -- let's hear yours!