The problem is that there probably are replacements. These targeted assasinations and the Stuxnet virus can slow things down, but not change the eventual outcome. To do that, you’ve got to lay waste to big facilities.
I was watching Al Jazerra last night, and apparently Iran is suffering a new virus called DuDu. I wonder if they know that means they are now in deep shxx. I tried to pull up the Google continuation on the story, but nothing came up but a title and a blank page.