That's an incredibly interesting thing in my opinion. Even if we send colony ships now, the odds of them arriving to a planet thousands years later that is already inhabited by humans or human descendents because our technology evolved over that time it non zero. Combined with relative time it gets even more weirder, because an almost-lightspeed ship we'd send could be surpassed by something much more advanced in a matter of days (spaceship time). So when do we send ships? I think there's a Kurzgesagt video about this somewhere