They're going to want to give us an "I am your father" moment for Episode VIII, just as they're giving (or perhaps "giving," depending on your tastes) us another planet-killer, another desert planet, another message hidden inside a droid, and so forth in TFA. Making an established villain from TFA the parent of one of the new heroes seems like the way to do that, and once you consider that part of Rey's backstory is that her parents vanished and she doesn't know where they went, and that Phasma is being carried over, AND that both Rey and Phasma have British accents when all the rest of the characters -- including those played by Brits -- have American and, well...those seem to me like the most obvious dots to connect.