I don't think we need to anything about population growth, except maybe have more children.  Throughout the history of the earth every organism has strived to spread itself, grow it's influence and dominate it's environment.  It's only natural.  Other than our level of self awareness, humanity is no different.  Like any lichen, algae, or virus, it's only a matter of time before it infects another host, in our case, a planet and eventually, another solar system.  It's hard to imagine technology that could allow us to reach another galaxy, but that's not out of the realm of possibilities, either.

At this point the only thing that can prevent or delay that from happening is a natural or man-made mass extinction event.  Regardless of what you think might happen in geo-political terms, we are past due for a natural mass extinction event.  As far as I'm concerned, over population of the earth is an opportunity, not a curse.

On the whole, humanity is an extraordinary organism.  The universe's way of becoming self-aware.  We may or may not be the only such organism, but here we are.