I doubt anyone could provide you with any meaningful statistics, but my feeling is that yes, it is probable.
There are several reasons for this. There has ever been a weapon created that has not been used. We like to see ourselves as tremendously sophisticated beings, and view science as sign of our enlightenment. In fact, science is simple tool that doesn't alter our morality. The invention of the rifle didn't make anyone sit back and consider the implications, it meant that now it was possible to kill people from further away. Same with the H-Bomb - the scientist's who built it may have turned around after it was tested and said, 'Oh pants, I hadn't really thought about the implications of actually doing this', but it didn't stop it being used on Hiroshima and Nagosaki.
During the cold war, there was at least the fragile comfort that neither side would be dumb enough to use these weapons as it would result in Mutually Assured Distruction (MAD). Now, however, with the defragmentation of the Soviet Union, and the fact that a frightening amount of essential radioactive material from their nuclear programme has gone missing, it is incredibly likely that other states/ organisations are working towards developing bombs.
Don't forget, a nuclear bomb may only have an effective range of a few metres - there are tatical nuclear weapons designed for use on the battlefield, for example. The technology is relatively unsophisticated - it's the materials that used to be hard to get hold of.