Notes on Mad ScientistsEvery book continues a Running Gag where we meet two Mad Scientists who study vampires, only one of whom will live to the next book. Candidates for the next one to show up:
When we finally meet vampire elder Joshua York, he will make references to Game of Thrones and Wild CardsLess a guess than a hope. Still, more oblique references have been made.
In-universe, drinking vampire blood will become the inspiration for the Rossum Corporation from DollhouseWe've already seem from Winthrop (and possibly Bond) that driving vampire blood can alter someone's personality. So in this universe imprinting will just be a matter of feeding someone vampire blood.
Dracula came to power because Sam Beckett accidentally leaps into one of Van Helsing's accomplices and screws upThere wasn't any indication of that happening in Dr. Seward's records, but then, he's going insane (maybe a result of being Leaped into?)