I think other space-faring cultures are extremely rare this early in the history of the universe. We are probably, for all practical purposes alone and may be for millennia.
We haven't seen any mass scale reworking of the galaxy around us, or we'd probably have seen some sign. I think that is best best hope still, looking for signs of a dyson swarm or even a ring-world type system. I saw hope. But I don't really have a hope either way about it. I do think it best humanity not have any contact with an alien civilization for the foreseeable future, but just being aware of the existance of one we could not communicate with would not be particularly harmful.
But yes some civilizations probably virtualize, population goes negative or does not expand enough to make travel necessary. A machine based civilization, especially one developed from organic life might reach the existential crisis of not evening caring, faster than an organic one. Maybe that will be out fate, if we survive this century.
They could go dormant, waiting for conditions to improve, but I think that unlikely. If this is a very early period for interstellar civilizations, than now would be the time to expand. You could go dormant, and awake to find someone else rearranged the galaxy to suit their needs in the 200 million years you've been dozing, or hiding out inside an event horizon (the latter idea taken from Fred Pohl's Heechee series).
A civilization with breakthrough phsyics allowing them to access and work with dark matter might find very little use for the baryonic universe altogether deal more with this and "mirror matter" if it exists.
Or there's always the exotic exit-stage-left option that they do find a way to open ways to parallel worlds and somehow exploit them, instead. A culture engaged in that activity would have minimal interest in space, beyond perhaps a small fringe group of enthusiasts, but they would not be empire builders.
