Some people say growth can't happen forever, and all growth comes at environmental cost, but that simply isn't true. I can create digital goods and services which people buy, and this increases GDP, and it doesn't hurt the environment and is indeed economic growth in the realest sense. I can even give massages all day, and this also doesn't destroy the environment.
There an upper bound created by the limits of possible human time spent. You can raise them with technology or population growth, but there again, you're bumping up against ecological constraints.
Population growth, yes, but technology? Why can't technology continue to improve in terms of efficiency and environmental impact as well as productivity?