How The Smoke Monster Dies! by JM

We have been told by MIB (in Locke form) that he cannot cross water. I think this is because he cannot physically touch water (he needs to be connected with the ground). Another instance of this is when Ben drains the water behind his coat closet and speaks to the smoke monster right before it attacks Keamy's group. He needed to get rid of the water before the smoke monster could rise above.

We also know that eventually the island will be under water because we saw it in the Season 6 premier.

My theory is that the smoke monster will be trapped somewhere on the island. Maybe he is trapped "in Locke form" so that someone can literally strap him down. Or maybe they trap MIB "in smoke form" with the sonic fence so that he cannot escape the region. Or maybe they use a circle of ash to enclose and trap him.

Then, to kill the smoke monster, the island will go under water. Being trapped physically or by a sonic fence or by ash, MIB will be trapped and will die when the entire ocean comes falling down upon him.

What I don't know is how the island gets underwater. But that is my theory on how the smoke monster will be destroyed.