Like if when Bowser in Mario Wii
Ideally we sort out nuclear power and climate change before anything, those are the most pressing issues and the most likely to Apocalypse Now us before anything else. We're not taking nearly enough action on the climate and if miraculously we can trudge through another 30-50 years without anyone firing anything nuclear than extreme imbalances with food and medicine shortages, overpopulation in the third world, economic downturn, etc, would likely push someone to that brink anyway.
I think the scrareiest of the doom situations is either a terrorist group getting nookems or the Indian/Pakistani situation taking a turn for the worst, because there's no clear solution to either of those and we're all just kind of holding our breath hoping some gay retard won't spiral us into a nuclear winter. If somehow we avoid all that then yeah space travel is the logical future step, but I honestly feel like we're so inevitably going to face some sort of unstabilising event that any of that is not gonna happen anytime soon.