I think the Earth will be there even after all the human race disappears but I guess when we die is the end of our world. Now 4 years for humans to vanish in normal conditions is just too soon in my opinion, but then a drastic weather change and natural disasters could easily kill us all anytime be it 4, 10, 20 years from now or next week.
What I don't believe is that we can say it just suddenly happened, we already have been given warnings, the possibility is not new.