It's possible intelligent species inevitably overcome/loose the desire for infinite self replication.
It's clear other animals will breed to occupy all available habitats. But it seems humans uniquely are developing the idea of the preserve in which environments are intentionally left unoccupied. I have even heard a tiny amount of talk questioning the impact of even a Mars landing. If that question is already coming up centuries before interstellar travel, one wonders what attitudes will be prevalent then.
Just a century ago it was quite desirable to intentionally release new species of bird's into new continents purely for aesthetic reasons. Now such an attitude would be abhorrent.
I suppose if one could demonstrate that the desire to endlessly replicate across the universe is somehow beneficial to individuals currently living then I imagine their values will embrace it. If endless self replication is not beneficial to the exiting population then they will eventually reason their way clear of that instinct and that reasoning will be integrated into their ethical code.
So while I, like most people reading this, am very excited by space exploration, that attitude may not be a permanent cultural characteristic.