Is Death An Absolute Certainty Or Not ?

Yes... Fact: "Everything dies eventually..." Cycle of life... and whatnot...
Dying is designed to make room for the next generation... It's perfectly logical..

If you really think about it, in the future they will easily be able to make it so that you can stay alive physically as long as you want to, for hundreds or thousands of years. What keeps you as you in the physical sense is your brain and your mind, so as long as they keep that in tact you will stay alive with your soul attached to that. They have already found how to stop cells from aging in mice and now humans, only a few more decades until it can actually be put into use in humans and perfected. Even without that they should be able to put you into a new body or keep you on support to keep you alive. My point is that even physical death, at some point in the near future, will not be certain.

I also have to say that there is no real "death" as we think of it. When your current physical body dies you simply "go to sleep" here and "wake up" somewhere else. This place would be in the spiritual world "ether" or "soul realm". Its kind of peaceful and relieving thinking about, at least for me.