Wouldn't it be the biggest TRAGEDY if our human species became extinct forever?

The sun is far off from exploding. It's a type G2V star, which means basically that it's a fairly average size for a star. Only larger stars tend to exhaust hydrogen fusion at relatively accelerated rates, but even then, if the earth was in orbit around an O or B type star, we'd probably not exist. We are part of an open star cluster, and a common characteristic of open star clusters is that the majority of stars are young (Cosmically speaking, of course). Yes, one day, the hydrogen within the core will be replaced with helium, and the sun will become a Red Giant, but we are far from that point...besides, we won't die from the sun exploding; we would die from it expanding...but the chances are much larger that we'll blow ourselves up before we could live for the millions of years it's going to take for that to happen.