After watching the trailer even I'm starting to believe it. Listen carefully to the voices. The main voice is Trevor, then you hear Simon say "That's the battle cross my father carried!" then you hear Trevor say "This I promise, you shall not stand alone against him".
Assuming he is talking to Simon and has retained his youth he's probably become Alucard. Now of course he could be talking to a character not yet revealed but I don't know. Right now my guess is that the four characters are Simon, Alucard, Trevor and maybe Gabriel.