If the sun is, one day, going to expand into a massive gigantic star and obliterate earth, then does that mean our galaxy wouldn't be...

It is true that our Sun is ultimately going to become a red giant and expand into a much larger size and engulf most of the planets of solar system. When that happens, the life on Earth will cease to exist. However, that eventuality is billions of years away. Our Sun is a relatively young star. Also, the question precludes the possibility of existence of life on other planets of the galaxy. We have so...

It is true that our Sun is ultimately going to become a red giant and expand into a much larger size and engulf most of the planets of solar system. When that happens, the life on Earth will cease to exist. However, that eventuality is billions of years away. Our Sun is a relatively young star. Also, the question precludes the possibility of existence of life on other planets of the galaxy. We have so far not found any evidence of life elsewhere in the universe, however, we may be able to find life on some other planet or galaxy before our Sun becomes a red giant. Thus, we cannot say (with much confidence) that life in our galaxy will become unsustainable. However, the solar system will not be able to support life once the Sun becomes a red giant. 

The artificial satellites in orbit around Earth have short lives (a few years); natural satellites (such as our Moon and those of Jupiter) will die out when the Sun expands. 

In general, the question is about an event that is a few billion years away and hence most of our answers are educated guesses, especially about the existence of life.

Hope this helps.