The issue is quite interesting and concerning as well. I, of course, see another war, this time with Iran, very unlikely. As you have stated, Iran and other nations alike are looking for nuclear weapons to empower themselves and there is little the United States can do about it.
For example, Dr. Khan, considered a national hero in Pakistan, was pardoned by the government for disclosing nuclear secrets. What did the U.S. do? Nothing. In fact, there was nothing it could do.
I always see diplomacy as the key to solve problems of this magnitude but as we all know, this doesn't always work. However, The United States can't fight on all fronts and try to make everyone cooperate. Let's face it, Iran is no Afghanistan, and it certainly is no Iraq.
If, and when Iran succeeds in developing a very strong nuclear arsenal, in a decade or less, there is little diplomacy can do, or even force for that matter. War has evolved so much that you just can't demand anyone anymore to comply, even if it is for the world's sake.
Another important thing mentioned is whether this inevitable growth in nations with nuclear weaponry capacity will either balance or unbalance the region. I believe that it balances by means of intimidation the whole region. But unfortunately, it also creates a very tense and unsafe environment. Somebody is going to loose control and eventually attack. Look at India and Pakistan, the only thing stopping each other from erasing themselves from the face of the earth with nuclear weapons is their nuclear arsenal itself. But tensions are there and are unavoidable.
I just hope that someday we finally get a break from all this and hear some good news.