Firstly i don’t think it matters if its Bin Laden or Al-zawahri who is the main evil behind Al qaeda all organisations governments and terror groups have there leaders but its not them who worry me the most,After all if there were to be caught Al qaeda would carry on and still be as dangerous,They are the figure heads of the organisation and have the final say on what they do but its the ones below them that plan what evil they do and put the people who do the attacks in place,either way i think it war on terror will go on and on through our lifetimes sadly.
As to the Nuclear threat this has been mentioned many times before it is a real threat but not one we can do much against i feel its better to be aware but live our lives the way we are ment to and not be intimidated by what can happen.