Mystic posted on twitter that the first boss's name is Asmodeus who is commonly associated with the deadly sin of Lust. He also pointed out that Asmodeus is classified as a major demon or a "Prince of Hell" by many.
The main princes according to Wikipedia are.
Lucifer: pride
Mammon: greed
Asmodeus: lust
Leviathan: envy
Beelzebub: gluttony
Satan: wrath
Belphegor: sloth
another interpretation is
Lucifer: pride
Beelzebub: envy (envious)
Sathanus: wrath (wraþþe)
Abaddon: sloth (slowȝ
Mammon: greed - avarice (avarouse) & covetousness (covetise)
Belphegor: gluttony (glotouns)
Asmodeus: lust (leccherouse) - later reported as using the name Asmodeum
but I think if this theory is right, they will use the top one.
First we have this guy
His appearance is remarkably similar to Beelzebub who has been in many SMT before
http://vignette1.wikia.nocookie.net...elzebub.jpg/revision/latest?cb=20090219082929
The fact that he is surrounded by money is usually an obvious sign of greed, but going with this interpretation he would be Gluttony.
Next we have this guy
who I believe turns into
I'm going to guess that he is Mammon/Greed. We know Yusuke's mentor was stealing/selling his paintings(at least I that was confirmed right? I remember reading something like that), which I first thought would be envy, but outright stealing and selling sounds more like Greed. I can't find a good depiction of Mammon to prove this would be it, but I'm guessing they are taking liberties.
Now for something I bet most people missed, in Hashino's interview you can see this scene
This is wild speculation, but the figure in the background looks like a boss to me. I'm proposing that is Belphegor/Sloth. The fact that it has people fighting for him, and he is sitting down, makes me assume this. Also SMT demon for good measure.
http://vignette3.wikia.nocookie.net...est/scale-to-width-down/250?cb=20080806040210
Next
Guessing this is another boss and obviously it's supposed to be sphinx. Going by what's left Satan or Leviathan would have to be it but not so sure about this one. Biggest problem in the theory. There are those two other terms that appeared with Morgana