Setting all religious beliefs aside... I honestly think it will come down to a game of cosmic billiards. Consider, for example
the Tunguska "event" in Siberia in 1908. Had that chunk of comet debris detonated a few hundred miles further west, we could have lost St. Petersburg altogether.
There are some large asteroids that will pass close to Earth in the next 40 years.
[Link to timeline] While we'll likely dodge them all for the forseeable future, I don't doubt that humanity will have to deal with the repercussions of a large-scale asteroid strike.
We already have a scale for use in quantifying the severity of the threat.
[Link to Torino Scale]
The question of survivablility depends on:
a) the size of the bogey and probability of collision.
b) the length of time between discovery and impact.
c) the technology we have at our disposal.