*If* Alucard and Simon really are one and the same person in LoS´ universe... well, here´s what I think how it could turn out:
In the old timeline, the son of Dracula used the alias "Alucard", Dracula backwards, to symbolize how he disagreed with his fathers methods.
So maybe, in the LoS timeline, Gabriels son, whatever he will be called, will choose the name of Belmont while opposing his father. Remember, Belmont was just a name Gabriel chose for himself... so this versions "Alucard" will use his fathers name before he became evil.