We live in all possible inhabitable continents (yes, we do live in Antarctica to some extent, but with advanced technology to aid us, unless -40 degree temperatures are natural for us). We also have developed medicine which cures/manages diseases that otherwise would thin our numbers.
So given basic evolutionary theory, there are few new environments for us to adapt to. Perhaps the next step in our evolution will be akin to how we became behaviourally modern, as in a rapid genetic mutation that quickly spread amongst us.