From what I can read about the smallpox virus, and the vaccine for it; we no longer have a vaccine for the virus; and once you get smallpox, there is no real treatment for it except to let it run its course. The reason it was called smallpox was to differentiate it from great pox, which is syphillis.
It has been killing people for thousands of years with no way of stopping it; so why would we want to take a chance of it somehow "getting loose" and casuing an epidemic for which we hve no vaccine.
The virus samples that they are talking about destroying are at present being kept by the United States and Russia; so that speaks volumes about the virus actually being saved to be used as a biological weapon by one or both countries.
Apparently , it has been used in warfare for at least the last 500 years, and was brought to the Americas by the Spanish in the 1500's and almost destroyed the Indian tribes, who had NO resistance to it. Imagine what it would do if it were released into countries now, who have no resistance and no way to cure it.
I doubt that the vials will be destroyed; not because the might be valuable, but because of the cold war between the United States and Russia. Neither side can be sure that the other side has truly destroyed the virus, so even if they claim they did, they won't.
I think that we have had enough years to study it, that if it were going to be useful for anything good, they would have already been working on that.
Look at these pictures of what happens to people who get smallpox, and imagine what it would be like if it spreads worlwide again.
http://en.m.wikipedia.org/wiki/Smallpox