Do you think the Earth will last forever?
When the sun turns into a big bright red giant do you think it will swallow up the earth?
Obviously it could melt and evaporate all the oceans etc, but the planet might survive, even if most of us dont.
Colonising other planets is an idea, but it would only save us, not our planet.
Do you think our planet is on borrowed time, or it will last forever?
Will a commet eventually get it if nothing else does?
If nature is allowed to run its course, they yes, the Sun will swallow the Earth and that will be it, I don't think anything useful will remain.
However, a civilization few billions years old should be advanced enough to do something about it, long before that happens