We should have guessed that warp drives and FTL is possible, since we've seen artefacts, instances of where natural objects under extreme conditions have gone supra-light. There is a black hole galaxy, or rather two merged galaxies, where the supermassive black holes are doing a dance around each other, and producing a super-luminal jet of plasma. Of course we can't see it until it slows down to light speed... but the fact there's a gap along it's trajectory is indication enough.