Few weeks ago I was very honored to be asked to try to tell the future of social impact design for the Impact Design Hub. Here's my prediction:
In ten years, social impact designers have found a way to prove the the positive impacts of design and it has become a norm to design (at least in the western cities) in a positive social way: to create spaces that increase cohesion and social interaction.
Considering social issues, social impact has become an issue for the majority of designers instead of a specialized minority. Of course, currently most designers try to create best possible social environments, but in ten years this aim has become genuine and also fact-based, instead of being merely intuitive.
Designers have also been able to develop (for example software) tools to facilitate more data in the building and planning processes, including most importantly citizen participation and consideration of aspects of environmental psychology.
Public interest design is not something that you specifically do, but an aspect that all designers consider in their daily work, just as environmental aspects have become a norm.
Read all the predictions of the other 17 inspiring designers at http://www.impactdesignhub.org/2014/08/27/feature-how-will-public-interest-design-look-in-2024-18-practitioners-weigh-in/