Is there already a civilization like the Observers somewhere in our galaxy?
Far from being unlikely, the existence of such a civilization is a natural consequence of the laws of computer science. The Drake equation L-value of the Observers is essentially infinite, with signals theoretically detectable but far below the threshold of SETI detectors.
The most advanced such robotic civilizations are probably recording and studying the history of the universe--a challenge uniquely complex enough to force them to continue to evolve as societies. Within a few hundred years we will be able to create our own version of the Observers. There are many possible ways this could happen. The Avatars Remember Nothing gives just one possibility.
As the universe ages and expands, civilizations of intelligent biologically-evolved beings will become more isolated in space-time. Their only hope of learning about the early development of our universe may be from contacts with robotic guardians of history such as the Observers.
See the Author's Notes for The Observers for more discussion (p. 163 of free pdf download, p. 147 of paperback).