On one hand, the self-annihilation idea implies that super-predator civilizations, being extremely rate to exist, would not have strong motivations for exterminating competitors.
What would possibly be the need, given the vastness of time and space, and the thermodynamic arguments given? Indeed, following this logic, the extraordinarily rare galactic survivor civilizations are almost guaranteed a long, peaceful existence.
On the other hand, it all develops on the curve of the galactic gaussian justifying possible pre-emptive defense investments. There's a difference of 3-4 or n sigmas statistics likelihood. In the former case, the likelihood of a rare rival emerging is high enough that pre-emptive defense strategies will be considered, and rudimentary systems of deterrence put in place. In the (high) n theory, it probably would not. How a civilization in the early stages of hegemony determined this fact, would be an interesting and possible civilization-saving (or destroying) feat....
Side note, haven't heard of the Revelation Space trilogy. Does it offer a workable theory for the origins of the predator dynamic?