The Galactic black hole has been known for decades. In fact, we know there are more than one (but only one is "supermassive").
What the astronomers finally did is get direct visual evidence (images) showing gas orbiting -- and falling into -- the black hole. Until then, all we had was indirect evidence -- for example, calculating orbits of the stars closest to the suspect black hole.
The black hole (or any black hole anywhere) is not "devouring" anything. Because it has gravity, things do fall into it. Stars in the Galaxy are on stable orbits and, therefore, are not falling into it.
IF (a big if) Earth were to succumb to the Galactic black hole, it would be in more than 3 BILLION years, after the "collision" between our Galaxy and the Andromeda galaxy. It is possible (albeit very improbable) that our Solar system would see its orbit changed in such a way that the whole thing falls into one of the two supermassive black holes (ours or Andromeda's). It is slightly more likely that we simply get ejected from the Galaxy (look up "Antennae galaxies"), which would change absolutely nothing to the life of the Solar system.
The most likely outcome is that our Solar system will simply become part of the newly formed elliptical galaxy that will be formed by the collision.
However, in 3 billion years, there will be no life on Earth (we will have lost all our water way before then).