Computer science and information theory were separate from physics. Not anymore. People realized that information had to be physical and this had profound consequences, especially in the form of quantum information/computation.
Psychology and economics were separate. Not anymore. People realized that humans were the core of economic systems and their behaviors fundamentally shape the nature of economies, even at the largest scales. Note the rise of behavioral economics.
Neuroscience and computer science were separate. Not anymore. People realized that thinking about the brain as a computer is probably the best possible abstraction to understand it.
Reality exists. There are no intrinsic boundaries in reality. All fields of study are created by humans. But these divisions seem so natural that nobody realizes that the boundaries have to dissolve. The fields have to collide. And when we realize that--or finally have the language and ideas to meaningfully talk about it--we find out all of kinds of crazy, cool stuff.
So: what collisions are we currently blind to?
The more we ignore the cognitive barriers we have placed upon the world, the greater our ability to problem solve. My own lab group (chemists and materials scientists) recently collaborated with microbiologists, civil engineers, and industrial engineers to produce a feed spacer which blocks biofouling in RO membranes using technology originally developed for use in medical devices using a catalytic process discovered by a nutritionist. It reduces biofouling by 3-5 logs, which is unprecedented, using a process that engineers never could have come up with had they remained focused on their own narrow field.
There is a reason that most universities are now encouraging collaboration between different departments.
It is useful to have specialized knowledge, of course, but we mustn't limit ourselves to our respective fields. Honestly, I think I would be against the creation of new fields of study at this point. Rather, people should be encouraged to work together with people of diverse backgrounds so we can apply what we have learned in one field to others.
As to the question, to pull a Rumsfeld, we have known unknowns and unknown unknowns. I could only guess at where the trend toward broad-based collaboration will lead us.