Long before the Sun burns up all its nuclear fuel and swells hotly to vaporize all life on Earth, humans will be long gone.
Every year the Sun ejects huge magnetised envelops of gases called CME's.
These Croronal Mass Ejections simply destroy all electricity when they contact such pulsing electrical waves.
Nature can support well under five billion people, the extra humans here are simply the oversupply that advanced technological civilisations can accumulate.
When we get hit by a solid CME the technology devastation will cause massive societal disruption and shut down essential things like water purification and food production.
Without advanced coordination medicines and transportation will simply be unable to stave off mass extinctions of human concentrations.

Billions will die out and the planet commence resetting itself, long before the billions of years the Sun will continue to glow in peace before it swells to gobble up the planet Earth we call home.

And; if your asking, CME's have hit Earth before and the effect was not fun...

/hugz ;)