The sun is indeed almost exactly halfway through its main sequence evolution, i.e., the nuclear fusion at its core is hydrogen to helium. At the end of this phase it will enter its red giant phase. When all the hydrogen is consumed the core will contract, becoming even hotter. When it reaches 100,000,000 degrees, helium fusion will begin, producing carbon and entering into the next phase. However, the sun does not remain constant during these phases. It has been steadily heating up during its main sequence--note my previous reminder that the earth's surface is much warmer than it used to be, which is probably the reason that land-based life only evolved in the last billion years. It will continue to get warmer as it burns up all of its hydrogen, boiling all the water off of this planet and making life impossible only one billion years from now. And it will slowly expand into its red giant phase, engulfing Mercury and Venus, and possibly Earth, by the time the hydrogen is gone. So it is not the sun that's going anywhere. It's the earth.