The purge will still happen, Ben isn't dead. The system will course correct itself.
1) Ben is still alive, and the Others will save him (I've heard the idea that Jack will, since he does in the future, but I think that's cheesy). I also think that the bullet will be the cause of Ben's spinal tumor
2) The Others clearly (and honestly) state that they have no clue who Sayid is, so Ben assumes it was a Dharma plot, and begins his hate for the Dharma people (right now, he just hates his dad). This will eventually be the catalyst for the Purge.
3) One of the Losties will be the cause of the Incident, which creates the button, and the electromagnetic pulse that brings them to the Island in the first place.
Basically, the Losties in 1977 will inadvertently and quietly begin all of the events that eventually cause them to crash there, hear the recording, meet who they meet, do what they do, etc. They start the timelines that end in 2004-2007, which they're tied into.
Also, right about now (in 1977), the construction crew is unearthing the Donkey Wheel for the first time. We know that Faraday was there when it happened. Sawyer, Faraday, Miles and Juliet all know where it is, and what it does. They will use it (probably mid-Season 6) to push themselves forward to 2007, to be reacquainted with Sun, Ben and Locke. I wouldn't be surprised if them using it is the cause for the Incident
Also, as for the statue. I truely believe it is just put in there for fun, so the writers can mindf$$k the viewers. It has no purpose beyond that, and the face on it is no one that we know. We'll see it one more time in some format, right before the show ends. I'll make a guess that it will be a painting, pencil sketch, carving, something like that on the shelf in the office of the person who is sitting on the mainland, who greets everyone the last time when they get off the Island on the very last show.
Put yer money down now, I have Vegas working the odds for my claim
