With Jacob dead, there is little left to stop Smokey from wiping out all those on the Island who stand in his way. If a small army of Others can't stop him, I'm not sure how the remaining Losties will be successful. Even if Smokey is not able to directly hurt the Candidates, his new army can, and I think that many of the people on the Island who we have come to care about (Jack, Kate, Hurley, Ben, etc) are toast. Perhaps whoever is coming to the Island (Desmond? Widmore?) will be able to prevent Smokey from leaving, at least for a while, but it will be increasingly clear that Smokey is in control and it will be only a matter of time before he can escape the Island to wreak havoc in the world. I am guessing that all the Candidates must be killed or claimed by Smokey in order for him to escape.
So what about the ALT Losties? The only reason we would be watching them live their lives in the alternate reality is if they are going to make it back to the Island. This is the significance of the hydrogen bomb explosion that ostensibly created a split reality for the Oceanic 815. This alternative reality, in effect, has created "spare" copies of the Candidates. All the Candidates are killed on the Island, but the Candidates still live in the ALT reality. So how do they get back to the Island? I would guess that Ms. Hawking exits in, and is aware of, the ALT reality. It is clear that the paths of the ALT Losties already are crossing. Ms. Hawking will find a way to bring them back to the Island (to replaced the Candidates that were killed), and successfully reign in Smokey before he escapes.