In reality scientist know from studying the life span of stars. We have billions of years left in our average size star. The Sun will swell and BBQ us then swallow us in its Red Giant phase before it " burps" off its layers of gases and becomes a White Dwarf about the size of Earth.
God says no one will know when he when jesus returns. Although in the bible there are seven things god says that will happen before he returns. 4 have already happened and the last 3 are planned to happen within our life time. I think these next couple decades are about to get crazy.
Well, the sun is predicted to turn into a red giant in about 7 billion years, so that would be the end of us.... except for the fact that I believe God is going to come sooner. (Biblically speaking, we're in the last era/church thingy and the world has gotten pretty messed up sooo.... yeah.)