Jacks future vision. I think it's just a glimpse of what COULD happen if they were to leave the Island now. It's not set in stone.
The coffin. I saw a screen cap of the Obit. It said something like Los Angeles man found dead, and the dead persons name started with J. So it could be Locke, Sawyer, Jin, or someone we haven't even met yet.
The HIM kate had to go back to...well they've been making us believe that Kate is pregnant, and I think that HIM is Kate & Sawyer's son.
The 40 yr old woman and her 8 yr old son in the car wreck? I believe it to be Juliette's sister and nephew.
I don't think Walt was really there. I agree with whomever said it was another manefestation. like when hurly saw his friend from the mental hospital, or when Jack saw his father.
One thing has been bugging me at the back of my mind since season 1. When Jack was in the caves he found his fathers coffin. He busted it up, and the coffin was empty. Did Christians body get left behind in sydney? I want to know what happened to his body.
I also still don't believe Michael and Walt were really allowed to go home. I think it was a trap for them and they're locked away somewhere.
I also really want Jack to discover that Claire is his sister.