A colonized civilization that still had contact between its various planets could still be wiped out by a plague or a sufficiently widespread war. Or they could commit mass suicide. Or they could be attacked and killed each and every one by another alien species. Why are you making such confident, general statements about a huge potential class of forms of life you have not met?
Well, let's take each objection in turn:
various planets could still be wiped out by a plague or a sufficiently widespread war.
The wave of expansion would travel faster than war, or at least at roughly the same speed. The dynamics of war in an infinite space seem to look like Hanson's hardscrapple frontier - everyone trying to move into new territory as quickly as possible. I'm not sure what you mean by plague, but it would have to travel outwards and might struggle to catch the expansion.
Or they could commit mass suicide.
Possible, but that seems...
An uplifting message as we enter the new year, quoted from Edge.org:
A few thoughts: when considering the heavy skepticism that the singularity hypothesis receives, it is important to remember that there is a much weaker hypothesis, highlighted here by Tegmark, that still has extremely counter-intuitive implications about our place in spacetime; one might call it the bottleneck hypothesis - the hypothesis that 21st century humanity occupies a pivotal place in the evolution of the universe, simply because we may well be a part of the small space/time window during which it is decided whether earth-originating life will colonize the universe or not.
The bottleneck hypothesis is weaker than the singularity hypothesis - we can be at the bottleneck even if smarter-than-human AI is impossible or extremely impractical, but if smarter-than-human AI is possible and reasonably practical, then we are surely at the bottleneck of the universe. The bottleneck hypothesis is based upon less controversial science than the singularity hypothesis, and is robust to different assumptions about what is feasible in an engineering sense (AI/no AI, ems/no ems, nuclear rockets/generation ships/cryonics advances, etc) so might be accepted by a larger number of people.
Related is Hanson's "Dream Time" idea.