For Christ to have a second coming, obviously there has to be an extant human race at the time, or there’d be no point. So God is not going to wipe out the human race beforehand (although my understanding is that at the second coming, the current universe will disappear).
However I think He is quite prepared to let us go through dire straits if necessary. I’ve long thought He intends to drive us off the planet, and out into the universe. My own personal quirk is that transport will be via quantum teleportation, as rocketry is far too slow. Scientists are fooling around with it already, in a very small way.
For example a recent link -
unsw.edu.au/news/pad/articles/2011/apr/Quantum_teleport_paper.html
Purists might think that there’s no mention of this in the Bible, but the reality is that computers, robots, space shuttles, space medicine, Hubble telescopes and all the rest are not mentioned in the Bible either. Yet they exist.
I think there’s a lot of trouble coming, and have thought so for years. In fact I’m surprised it hasn’t happened already. I could nominate several potential flashpoints even now (India / Pakistan, North / South Korea, Middle East), and factors which would exacerbate them (Western debt, population pressures and resource issues, China and India as emerging superpowers, the still formidable nuclear arsenals of the US and USSR, technology which could be used to monitor people, the global village, the resurgence of Islam, the fact the Moslems have control over so much of the world’s oil etc.).
So when the stuff does hit the fan, it’s going to be one almighty mess. But there will be a surviving remnant. There always is. Until the second coming - then it will be over.