Ok Oasis For the Four mobs Dragons were confirmed to be added. so thats 3, and The NPC villages? I think you need a mob as an NPC for them :P
I'm about to unravel at the stupidity that is you:
"At least one new mob"[11]
New Enderman mob. [12][13]
That's the only new mob related planned features.
Now, once again, I'm pretty good at math, and from here I can count roughly 2 mobs talked about. We have a skin for a "silverfish" and pictures of Enderman. No dragon pictures, no critter/water creatures (depending on what the silverfish actually is.)
So if you'd be on your way now. And as for the NPC villages:
It is unknown at this time what kind of NPC's will spawn around and in the buildings. It will however most likely be Humans or living Pigmen.
Though it is unknown at this point, it still concludes that there are 2 planned mobs for the adventure update.
Poll