Barry Rubin is sure that the Israelis will not attack Iran's nuclear sites this year, and offers various reasons (pro-Israel reasons, by the way) why an attack shouldn't happen. It's a very interesting essay; read the whole thing:
Why should Israel attack Iran now? Because one day Iran will have nuclear weapons that might be used to attack Israel.
Does Iran have such deliverable weapons now? No.
If Israel attacks Iran now does that mean Iran would never get nuclear weapons? No, it would merely postpone that outcome for at most a year or two more than it would take otherwise. And then it would ensure an all-out endless bloody war thereafter.
If Israel attacks Iranian nuclear installations would that ensure future peace between the two countries? Would it make it less likely that the Tehran regime uses such weapons to strike at Israel in future? No. On the contrary, it would have the exact opposite effect. Again, it would ensure direct warfare between the two countries and make Iran's use of nuclear weapons against Israel 100 percent probable.