20-Year Prospect
Let's be honest: we've gone through booming times, but what we're in right now global-economy-wise can no longer be described as such. That means new cities aren't popping up like so much popcorn, and we don't need a megamall for every 200-person township. There aren't as many obvious opportunities for a humble real estate developer to start developing, so he or she will have to do a little digging.
However, the population is still growing, especially in parts of the world like China and India. In addition to the expansion of population, the technological advancement of society drives the need for better resources to be built for growing communities.
In places like the U.S. and Canada, more and more people are moving to the urban centers, requiring more development in city centers and once-neglected neighborhoods. There does seem, however, to be less interest in urban sprawl, thus presenting new challenges for developers to build up rather than out.
Essentially, the world is in a new and interesting state of flux. But because it continues to grow, it'll still need people with the vision to create space for the coming generations. This job will certainly be around for twenty years, but we can't guarantee how easy it will be to make a living at it.