The next new media is something really hard to define. Like Steve Jobs said people don't know they want something until you've shown them. We have many social media sites that bring together all types of people. From dating sites to selling your items there are too many to count for various things.
A new media would have to be something that would bring at least a million people to the site with a common interest or bring those people together to work towards a common goal.
The new media could be a site for tenants of a building to talk to each other and post problems in their apartments. The site could also be used to rate the building in terms of whether or not the building or the surrounding area is good. It could also be used to help people move in or out of the building.
Another possible new media could be a site for business owners in the area to talk to each other and figure out ways to bring in more customers. It would benefit all of businesses in the area to work together so that they can all increase their profits and increase their range of business to other areas. The possibilities are endless and you can't really pinpoint something that will be successful until it is actually put into place