Well. Truth is, I have no idea. You could look at it from multiple religious perspectives and estimate when doomsday will occur, but the problem with that is that calculations are always wrong.. Which is to be expected, considering most of these religions are governed by humans and not by Higher Beings itself. Humans are filled with imperfections and errors.
On the other hand, you can also look at it from the perspective of the current state of humanity. One could argue that if we continue our wars and exhaust our natural minerals and wildlife, the human race could die out a lot sooner than most would expect. That's not even including diseases. Personally, I don't think it'll go out in our lifetimes, however that depends on where the world heads in the next few years. And since science is working on extending the human lifespan, this could be a more important issue if folks end up dying at 500 years old or so.