Fundamentally, for Iran it is irrelevant whether they can make a nuke or not. All that matters is that they convince the West, and more importantly their Arab neighbors, that they have the capacity. This would give them enormous "street-cred" in the Moslem world, the leadership of which they are ever seeking. Israel is only a side-show in this ridiculous pissing-contest that the Iranians have been holding water for years to win.
They will not likely have the capacity for decades, but may bluff their way into a showdown, which they believe they have the cahones to win. Fortunately, their security is as porous as a seive. We know what they're up to, hence the two major military forces present to their east and west. So we (Westerners) hold all the cards, and can call their bluff.