Our descendants will look back on us with some horror: an era of peoples who could have largely saved themselves from oblivion, but didn't. Suicidal, negligent barbarians they'll call us - and they'll be right. We have had the tools to preserve the brains of the dead for the long haul for quite some time now, and preserve them well enough that the fine structures storing the data of the mind remain intact. Death is death, but oblivion only occurs when the present detailed arrangement of matter in your brain is destroyed. For so long as that data is preserved, there is the chance that future technology and circumstances will lead to a restoration of life, such as through the use of advanced nanotechnology and charitable groups dedicated to returning the preserved to active life once more.
The preserved have all the time in the world to wait, after all.
When we are stirred to think of it, we have a sort of horrified sympathy for our distant ancestors: peoples who lived brutish, painful, and shorter lives because they had no choice. Many thinkers of past ages envisaged a better world and better lives, with no hope of seeing that transpire with their own eyes. The same sentiment will be applied by our descendants to those who came a little way before us: doomed generations who could grasp at ideals and possibilities, but had no practical way to achieve these ends. Consider the words of Benjamin Franklin, for example:
I wish it were possible... to invent a method of embalming drowned persons, in such a manner that they might be recalled to life at any period, however distant; for having a very ardent desire to see and observe the state of America a hundred years hence, I should prefer to an ordinary death, being immersed with a few friends in a cask of Madeira, until that time, then to be recalled to life by the solar warmth of my dear country! But... in all probability, we live in a century too little advanced, and too near the infancy of science, to see such an art brought in our time to its perfection...
Sympathy is appropriate for those with high ideals and no possibility of ever achieving them - simply born too soon. But what of those who could achieve but turn aside and shirk the task? That would be us. I'd say we and our immediate forebears became suicidal, negligent barbarians about ten years after it became possible to build an industry to preserve brains, with a cost at scale that was affordable to the masses - on a par with funerals, for example.
For preservation methods along the lines of plastination, that point probably came and went somewhere in the 1930s or early 1940s, with the growth of the chemical industry into a true giant. The 1930s also saw the development of the first electron microscopes, and life scientists of the time arguably possessed enough knowledge of the cell to make educated guesses about which forms of chemical or low-temperature preservation would retain the data of the mind.
Here we stand, three generations removed, a thousand distinct human cultures in which there is little to show that we desire anything other than oblivion or self-delusion when it comes to our lives. Judging by actions rather than words, people who greatly desire both lasting life and health are a minority indeed. And with each passing year, another fifty million lives vanish into the maw to be destroyed utterly.