We have only gotten as far as this due to our tech keeping pace with population. At some point our tech will fail be it by natural disaster or just the limits of exponential growth.
Nature seems to have an overpopulation machanic built in. When a species becomes to much of a burden on environmental resources it is usually put back into balance from disease or food shortage. Our tech has kept up with both so far but imo it will hit a wall at some point.
I dont see us ever colonizing other planets if we cant come up with anything better than fuel propelled rockets.