It seems to me that it is a safe bet that the known limitations of Physics will never be overcome, to such an extent that we will be able to dominate the galaxy. I.e. FTL travel doesn't seem like it will ever be more than science fiction. Many phenomena are governed by a dipole curve, where things start slowly, then hit a tipping point where they rapidly accelerate until they reach a new level of stability. You see this in economics, in Physics / Chemistry, in the evolution of new species, etc.
Why are we alone then? If alien civilizations had arisen 1 billion years before ours, and developed technology beyond our dreams, wouldn't they at least leave a trail of some kind?
Something to consider is that radioactivity decreases with the age of the universe. There is a certain probability that a % of an element will be a radioactive isotope when such elements are created. Less and less heavy elements are being created as the universe ages, and existing ones decay. This means that life will arise more easily.