I still wonder who the final boss will be in this game. At first I thought it might be Zobek. Like you defeat Satan and all and since his worst rival is no danger any longer Zobek can now try to rule. However, after these informations about the game got leaked I doubt it. I still think that Zobek will be a boss in this game (also having a Death form) but I doubt he's going to be the final boss.
I also doubt that Satan will be the final boss as he already has played this role in LOS 1. I assume one of the following ideas:
1.) It's the Leviathan, as he was mentioned in the leaked informations. Many have theorized that Leviathan would be the name of Satans transformed appearance. However, I doubt that, simply because a creature called Leviathan was mentioned in the Reverie DLC (Chapter 13-2). It spoke of a giant creature, an old god sleeping under the castle called the Leviathan. Though I wonder why this creature should be the final boss for this trilogy. So even if he won't be the final boss of LOS 2 I hope that he will at least appear as a Titan battle.
2.) It's Dracula as a Lord of Shadow. After fighting Satan Gabriel will ascend as did the three founding Members of the Brotherhood. Since Gabriel needs both light and darkness/ shadow in order to fight Satan he must not only reaquire his old abilities as Prince of Darkness but also find the good side of himself, that still slumbers deep within his soul. Either during or after the confrontation with Satan Gabriel might ascend leaving behind his dark side, giving birth to "the real Dracula", a proper Lord of Shadows. So in the end the ascended Gabriel must return one last time to earth in order to fight his dark self, which has two forms: the human Dracula form and the Dragon form.
Then again an ascended Gabriel would have to have totally different abilities since he would no longer be a vampire. A second reason why this might not happen is the fact that maybe Mercury Steam while seeing their game as the end of the trilogy might want to make Dracula survive (even if it is him as a Lord of Shadow as described above) somehow and thus give other studios the chance to make their own CV game being located in the LOS universe.
So even though it certainly has been discussed somehwere among the 300 pages of this thread, who do you think will end up being the final boss? What do you think of these two theories that I have listed here?