We will destroy this planet. Thats a garauntee. Good news is, we'll most likely find a hospitable planet or terraform one before the point of no return for humans. Earth is fucked though because the more technology we develop, the more possibilities for the destruction of this planet crop up. Technology is a double edged sword.
While the chances of this are low right now, within the next two hundred years it becomes close to 100%. Scary huh? Thing is, we'll be able to leave by then, so its alright.
On the question of war, yeah. Its gonna happen as long as humans are alive. Its retarded, but yeah.