We might be able to make a prediction, but I doubt it will be very precise or that the prediction will be in a realistically short time frame (I would suspect any event in the Milky Way predicted to happen after the merger of Milky Way and Andromeda to be pretty speculative). The Hulse-Taylor binary pulsar has an orbital period of less than 8 hours and already has an expected life time of 300 million years. S2 would have an orbital period of about 6 days if it orbited in a circular orbit at its current closest approach distance. And as far as I know, the expected life time increases super-linearly with the orbital period, so the expected life time would probably be at least 5 billion years.
They are not very strong actually. Small black holes have much larger tidal forces near their event horizon than large black holes. That means that large black holes can be "quiet", i.e. they can swallow stars without tearing them apart before they reach the event horizon. Small black holes tend to be "louder" - they tear apart their prey, squeeze them into a giant accretion disc and then eat that disc piecemeal, meanwhile producing a lot of radiation via this accretion disc.
