An interesting analysis that lends support to the idea of decreasing crime over time:
http://marginalrevolution.com/marginalrevolution/2011/06/long-term-trend-in-homicide-rates.html
Steven Pinker also writes a lot about this. A short summary of what I gather from his work is that, even today, criminologists cannot explain very well why crimes rates rise or fall over time. There are many theories, such as the development of Jurisprudence (nonviolent alternatives to dispute resolution), increasing affluence (more to lose and less to gain from crime), and exotic ideas such as phasing out leaded gasoline (lead is a known neurotoxin that can cause aggression). I have yet to see what to me is a convincing explanation of why some OECD countries have much higher crime rates than others.
In the future, crime (or activities classified as such by governments) could be driven by a variety of factors. There is
disturbing evidence that freedom in the world is leveling off or even going into decline, which could provoke dissatisfaction. Governments, rebels, and criminals also exist in a kind of arms race, where the growth of power on one side is countered by new measures on the other. In particular, criminal organizations can now operate more easily than ever before on an international scale, greatly helped by modern telecommunications and the existence of failed states or ungoverned or badly governed regions. It's reached the point where most people in the world are more threatened by civil conflict, drug conflict, human trafficking, or terrorists than they are by other nation states.
Circling all this back to C2C, it makes sense for crime to play a declining role as the game progresses, but it may also change form, and it should not be expected to go away any time soon. For the most part I like how it functions, but one thing I don't like is the emphasis on big stacks of policing units. It can turn crime management into a one-dimensional picture of forceful suppression, which ignores many dimensions of how law and order function. If it wouldn't unbalance things too much, perhaps we could nerf the law enforcement units (or somehow implement a system of diminishing returns on them) to force a little more creativity in managing crime.