Welcome to Gaia! ::

It is assumed that in 5.4 billion years our sun will become a red giant slowly causing every planet in our solar system to collapse, leaving only a cloud of dust behind. If this does not happen I have other other guesses on how we might die.
1. Our O-zone layer will fall apart making beloved Earth a lava planet and destroying us all.
2. War and killing leaving only several people behind who will eventually die. (unlikely.)
3. For a giant sun-flare to occur and kill all living things dead and burning.
Do you have any other guesses? If so, come out and share em'.

^^ thats true.

I think power will get the better of us, when the world is destroyed, we will move onto another planet and consume that. nothing but a bunch of locusts.

as to how? nuclear weapon? lack of diversity? a disease that we are not resistant to in the slightest. HIV and Aids

The Ozone one is interesting...Yes it would cause one deadly sunburn...At the same time a couple of Summer's ago NASA, the NSIDC and various other organizations that monitor global sea ice indicated that the ozone hole over Antarctica, while letting more UV rays in, somehow let all heat escape. This led to the Antarctic Sea Ice growing to it's largest extent in recorded history. I believe it was Summer of '07 when it happened.