Here are my theories:
1) The moon will crash into the planet in exactly 3 days.
2) A stupid fish will wake up, taking this entire dream with it.
3) A very eccentric teenage high school girl will get annoyed and giant blue blobby things will destroy everything.
4) A silver-haired maniac will send a meteor into the planet.
*Stares coldly at someone on the forum.*5) Many many nukes go off and turn the world into a nuclear waste land where people were kept in vaults...or something.
Okay, seriously, I don't really believe in dooms-day theories. If the world were to end tomorrow, I'd honestly rather not know about it so that if it were to happen, I wouldn't know until it was too late. This way, I just go on living life normally for however long there is. Of course, that's just me.

As for the long run...I dunno. I never really try to think about the end of the world, as I said above. It's just something I don't think about.