Alucard having a son will be on the same level as Wesker having Jake in RE and Vergil having Nero in DMC. "This guy had sex? This guy?!"
EDIT: Jokes aside, the Belmont's Curse announcement does make me realize how significant Alucard having a child--- and more importantly, Dracula having a grandchild--- would be. Belmonts get successors all the time. Alucard continuing the very bloodline he swore not to perpetuate? Unthinkable... but exactly the kind of lore-breaking premise future games just might use.