There are a few possible solutions.
Innovation: a long shot, I admit, but if some of us have lofty goals such as terraforming Mars, we could certainly develop new methods of producing goods and foodstuff in more efficient ways. Personally, I believe that there is no limit to human ingenuity.
Space: self explanatory, really.
Wait for the War to End all Wars: The most cynical, and sadly the most realistic. There wont be Seven Seals, or a Great Beast, but with population rising and resources dwindling, people will prioritize their own interests and take whatever land, water, and resources their country needs to survive. On the bright side, this will be a War for something dire, and not a spectacularly bad case of anti-Semitism. *inb4godwinslaw*
Good old Mother Nature: Eventually, nature takes care of overpopulation. In our modern world, illness can spread world wide in a matter of weeks. As with Europe's Black Plague, a huge chunk of the world population will die. The ones that are left will be able to pick up where we started. Our technology is unlikely to die as a result, so in the grand scale of things it will be like nothing ever happened (except the whole "1/3 of the population gone, bit)
EDIT:
Point is, one of the four will happen. Overpopulation is a problem that literally solves itself, sometimes brutally so. Contribute to innovation or space travel if you like/can. The rest of you can cross your fingers and enjoy the ride.