Its possible that medical advancements in our lifetime mean we are around for it. not likely ...but not ruled out completely... worse....the asteroid happens into a wormhole and pops up on our doorstep 100+ years earlier ... hurtling towards us screaming "Surprise!!" not likely... more likely ...a hybrid Dave-like theory....will occur... which naturally includes aliens.. https://www.youtube.com/watch?v=G7uHDitVce0