[r2_pilot]

The physical continuing expansion of the universe eventually causes any photon to be so far redshifted as to be unobservable, so it actually goes the opposite way. One day long from now, an alien civilization might look out into their night sky and only see their galaxy, and be completely unable to tell the previous history of the universe from observing the sky.

[Sanzig]

There's also a possibility that a sizeable fraction of all stars exist in the intergalactic medium [1], having been ejected from the galaxies where they formed due to galactic collisions or encounters with their original galaxy's supermassive black hole. A civilization evolving around one of these stars in the far future would be totally unaware of the universe outside their own solar system due to cosmic expansion.

[1] https://en.wikipedia.org/wiki/Intergalactic_star