it's not like his origin can be too surprising anyway. It's likely only one of a few possibilities
The Classic origin, albeit tweaked for the LoSverse,
Trevorcard, (though it seems unlikelier and unlikelier, it's still a possibility)
Some kind of mirror produced... thing.
I doubt his origin will be too radically different. Considering Alucard being a MASSIVE fan favorite, if they botched him, it could potentially SINK MoF, and MS. It's simply in their best interest to be as smart as possible about Alucard.
So i seriously doubt it will be too drastic, it's not like RE6 where we did not know the new character.