The good news is:
“It is extremely unlikely that any wandering supermassive black hole will come close enough to our Sun to have any impact on our solar system,” said lead author Michael Tremmel, a postdoctoral fellow at the Yale Center for Astronomy and Astrophysics, in a press release. “We estimate that a close approach of one of these wanderers that is able to affect our solar system should occur every 100 billion years or so, or nearly 10 times the age of the universe.”
So, even though the supermassive black hole at the center of the Milky Way may have a dozen disenfranchised siblings, by the time they could pose a threat to Earth, the Sun will have likely already burnt out. In the meantime, astronomers will continue working hard to definitely prove these wandering Goliaths actually exist. And once they do, the real fun can begin.