Iraqi Kurdish leader Masoud Barzani wants to hold a referendum in October 2016 in an attempt to gain independence for Iraqi Kurdistan. Will this referendum make Iraqi Kurdistan a sovereign state? If not, how would Iraqi Kurdistan become a sovereign state?
A state is souvereign when other states accept it as such. Whether or not one accepts a state is usually a question of what's in ones political interest. You might want to look at Wikipedia's list of states with limited recognition and look at the backgrounds for more information about why a state would or would not recognize another state.
So if a Kurdistan state would be proclaimed, we can assume that those state(s) which currently claim(s) its territory would likely be hard-pressed to recognize it and also try to pressure others to not recognize it.
Supporters could be those who believe that the new Kurdish government will be easier to deal with than that of those who were there before. Who that could be is hard to say at the moment because we don't know yet how that hypothetical Kurdistan would position itself on the geopolitical landscape.