In all likliness we will just implement the sustainable tech we have into everyday life. Water isn't an issue - we've got plenty, as long as we have a way to filter it (and yes, I mean sea water as well). Food is by nature sustainable, we just need to get better about sustaining it. As long as there's sun, moving water, wind, etc, we will be fine electricity wise.
Im not saying life would be the same, but I doubt it would change as much as you might think.