Items for consideration (full disclosure I am wetting my pants over the possibility of THF being in game)
For:
- SE tends to like to surprise (SCH, Ultima HM from 2.1 was supposed to be a secret, late-ish patch notes, etc).
- The speculations that it is a caster have far less obviously visual support than the speculations that it is s THF.
- It is not very likely a caster because it seems to be in a forward-moving motions, rushing towards Leviathon, where as the casters depicted and leaning backwards, away from the main action. This would also support it NOT being a BRD.
- The off-hand is obscured, possibly holding a second dagger.
- If it were a THF, it is taking the place of BRD in that image, lending to the theory that THF would be the second support/dps class.
- Yoshi has talked a lot about him feeling that a scout/stealth character is missing from the game
- There was speculation that Yoshi wanted to add a new job before there was a level increase/expansion
- The major re-balancing of classes was done in 2.1, what has job team been doing in the interim?
- The Thancred portion of the trailer that mentioned new story quests clearly shows a more distinct affiliation with the THF class/job. (The other scions are JOBS not classes, leading me to believe this would hint at Thancred pre-cursing the THF JOB) He was clearly some kind of THF before with throwing knives and his agility, but dual wielding daggers with acrobatics and clearly attacking with them is a pretty clear flag that that's what he is. GLA can't dual wield, homies.
- It would lean towards rationality that if this is, indeed, a THF fighting Leviathon - then THF should be introduced in 2.2
- The Maelstrom and Limsa Lominsa are an excellent breeding ground for Thieves, a pirate-based culture, the home of some "finer things" (The Bismark, etc), and the fact that Limsa is only home to two starting classes, whereas Ul'Dah and Gridania house 3 classes each. (I know SCH/SMN makes it 3/3/3 in terms of Jobs)
- Might Corsair be a new Limsa class that would branch to the MSK/THF jobs?
Against:
- There is clearly no specific clarity that the character shown is THF.
- Even if it were wearing a T-Shirt that said "I got a THF to level 50 and all I got was this lousy T-Shirt," doesn't mean that THF will be in this patch.
- YoshiP was most recently quoted as saying that new classes and jobs would be released in an expansion, not a patch - I believe.
- A skirt on a THF is not very practical.
- The off-hand is obscured, so we don't really know what other distinguishing characteristic might be held therein.
- MSK guild is already in the game... There are a lot of indications that MSK should be the next new playable DoW/DoM introduced.
I know that I am kind of biased towards the "for" side, but the only real opposition to this speculation that I see is that it might be a different class. It really does not look like a BRD to me, a DRG would rarely if ever wear leather armor, and if its a caster I'll eat my hat.