It may be slightly too much to say that it is certain that Homo sapiens will become extinct in a time comparable to time that that species has existed but it is not, in my opinion, unscientific to say that the evidence is such that the odds are so strongly if favour of this happening that it should be accepted as a working hypothesis.

When this happens, bacteria, the real success story of evolution, as well as many other species will carry on as normal.

From a planetary perspective man's passing will not be of fundamental importance and from a cosmic perspective, and these religions tend to imply that their teachings have cosmic application, man's passing will be of utter insignificance.  

Peakguy is entirely correct that the mind set that so readily accepts all manner of improbable propositions in order to avoid acceptance of the oblivion facing him in a few decades is pre-conditioned to accept comforting stories that dismiss or minimise the problems threatening him and to do so in the face of all evidence to the contrary

Crocodile:

It's a religious belief because you are predicting the future with too much certainty, i.e. with a certainty requiring faith. The fact that the dinosaurs  became extinct due to a cosmic catastrophe does not prove that we are doomed to the same fate. We may be different from the dinosaurs. Only time will tell. The scientific position is agnostic: maybe we'll go extinct, maybe we won't. "Doomed" is a religious concept.

I would challenge you to point to a single animal species alive 100 million years ago that still exists in the same form today.

Alligators, army ants, cockroaches, the coelacanth, cycads, the dragonfly,the gingko, the horshoe crab, the nautilus, salamanders, the sturgeon.

Also, change and extinction are different things. If the human race survives by gradually morphing into something more mechanical (a la Ray Kurzweil and Hans Moravec), I wouldn't say the human race became extinct. There's a big difference between a lineage changing and perishing.