Are there any other well known events besides heat death of the universe that for sure will impact humanity?
but the gist is that Galaxies are mostly empty space; so even though the massive black holes in the center will eventually collide, most of the stars/planets/etc. will remain in unfazed.
Also in about 4-5 billion years, the sun is slated to reach the end of its life, at which point it will grow big and hot enough to destroy all life on earth (and possibly earth itself). This seems like it's more of an issue to be worried about.
See also: https://en.wikipedia.org/wiki/Future_of_Earth, https://en.wikipedia.org/wiki/Timeline_of_the_far_future
>> Excluding planetary engineering, by the time the two galaxies collide, the surface of the Earth will have already become far too hot for liquid water to exist, ending all terrestrial life; that is currently estimated to occur in about 0.5 to 1.5 billion years due to gradually increasing luminosity of the Sun; by the time of the collision, the Sun's luminosity will have risen by 35-40%, likely initiating a runaway greenhouse effect on the planet by this time.