Hey folks, I've just read part of the spoilers revealed by the user (from devilorg), who bought the magazine with the guide.
So far, he/she confirmed that there will be 6 bosses in the game.
The bosses are Hunter, Succubus, Bob Barbas, Killing Face ( aka Mundus spawn), Mundus and Vergil.
The description for the Mundus battle ( ipsis literis from the post that I read):
"No, there are 6 bosses confirmed by the booklet....Hunter...Succubus..Bob Barbas...Killingface(Mundus's baby)...Mundus and Vergil...also on Mundus it says that when you are fighting him you are on platforms and he attacks with his hands,fireballs a shockwave and spits some kind of lava from his mouth...also it says when you defeat one of his arms you demon pull in his eye to bring out Mundus and Vergil core (something fishy about that..maybe Mundus absorbed Vergil) It seem to me that Mundus is sadly that giant demon at Gamescom trailer...also it says his attacks do 2/3 damage....I still hope we fight him in his human form though Also Tammem has said that we will fight human sised bosses but as it seems nope"