It is very hard to predict the effects that smart phones will have on society. There are many impacts that may happen, but it is impossible to know for certain which ones will happen.
In the short term, smart phones seem to be affecting the ways in which we interact with other people. It is not unusual to see a group of people who are together physically, but who are not necessarily interacting with one another. They might all be looking at their phones and interacting with people who are not present. They might even be simply playing games and not interacting with anyone at all.
What this could mean is that we might experience a long term decline in the levels of cohesion in our society. If people do less interacting with one another in person, it is possible that we will become less adept at personal interactions. We will be less connected to the people around us and our society might become less closely tied together.
It is also possible that we will come to lose the idea that work and leisure are separate. We might be tempted to engage in leisure activities on our phones at work. On the other side of the coin, we may feel compelled to keep up with work activities on our smart phones at times when we are supposed to be having leisure time with our families.
However, it is impossible to know what impacts will actually be seen in the future.