If we don't achieve a technological singularity in the next couple decades, I doubt that an alien invasion will be a worry a couple centuries from now. I say this because of impending ecological collapse, which will end human civilization as we know it... if not humanity in total.

And I'll save for another time a rant about how expensive it is for anything to cross interstellar distances. At most we'll see a self-replicating probe that tries to subsume all matter in the solar system, the "invaders" won't physically travel here.