Our sun appears to be of medium size and medium age, having been in existence for about 5 to 6 billion years, and having another 7 to 8 billion years to go, at least as far as its nuclear reactions are concerned. The Sun, like all stars, is burning hydrogen, or actually fusing 4 hydrogen atoms at a time into 2 helium atoms, and giving off energy in the process. In several billion years, the hydrogen will run low, and the Sun will cool and expand, becoming a red giant, and at this point, billions of years in the future, the Sun will actually radiate more heat than it did because of the larger surface area, and life on Earth will end. But that won't be the end of the Sun! It'll begin burning helium, fusing it into carbon. When the helium runs low, the Sun will contract and the core will heat up, fusing carbon into oxygen and neon. Contraction will slowly continue, causing the neon to fuse into magnesium, which will fuse into silicon, which will fuse into iron, where the creation of elements through nuclear reactions ends. When the nuclear activity stops, the core will cool, and the Sun will suddenly (in about a second!) collapse into a relatively cool white dwarf, which it will remain for tens of billions of years, until it cools enough to barely radiate any energy, at which time it'll become a black dwarf.
The New Intelligent Man's Guide to Science, I. Asimov, 1965.
An interesting question. We can't be sure, of course, because we've only had the tools to observe the sun across a wide range of the electromagnetic spectrum for a short time, and therefore have only a limited snippet of the life span of a star. We have, however, observations of other suns, and these observations suggest the sun will slowly grow larger and run out of hydrogen in four to five billion years. It will grow in size, then shrink. It will end up quite small—probably a white dwarf.
It' s unlikely that people will be around then, and the sun should out last us by some time.
There are still billions of years left before the sun dies. It will either become a black hole, or expend and then become a white dwarf.
Our sun has survived only 5 billion years and more 7 billion years are there for the sun. If our sun has less mass than the chandrashekhar's limlit than the sn will become a blackhole or else if there is more mass, there will be a supernova and the sun will become a white dwarf.
At one point in an unknown time from now the sun coul go supernova and then collapse into a black hole.