In the bible, Jesus, St. Peter, the Revelation, and Isaiah (possibly others) state that Heaven and Earth will pass away. But Isaiah says that this earth - the things of this life- will never be remembered or brought to mind again, in the new Heaven and Earth. Find these things in the bible for yourself, so that you can get the sense of what is being spoken there. Personally, I think that these people are talking about the whole universe being destroyed. And not necessarily some gigantic distance in the future, like millions of years from now. But, rather, soon-ish, like possibly any day within the next 100 years, or so.