I think that you can easily make the arguement that that's what happens when people don't die. The morphic field kept them alive, but it didn't rejuvenate cells from what I saw. I kept them moreso at their current state. If you were already old and in deteriorating health, it didn't make you heal or get better (no one healed after being hurt after all) it just kept you from dying. So if you were in a near dead state, you just stayed that way.
I dont' think more people 'got' that way, they just found/showed more of them. There are 6 billion people in the world. If there was an even number of people of each age from 1-100, that'd mean there were 1.2B over the age of 80 in the world. Plenty enough to show what they had in 'near death' states. It's what they were talking about in the beginning about no one dying in that hospitals and hospices and whatever would have to take care of terminal people forever.
As for the burning, if you're just ashes I don't see how you'd still stay 'alive', miracle or not.
Holding a gun is still a threat because no one knows if it's permanent. If you're shot in the chest and the miracle ends...then what? Is it worse to die in an instant without warning or to know that you're mortally wounded and if the miracle ends, you're likely to drop dead right there?
Jack's blood made the 'blessing' emit a field that kept people alive, not one that changed their physical makeup. Prior to having his blood introduced it absorbed the blood(?) from the people living at each end so that their life expectancy was dead on equal to that the 'average' life expectancy of the time. His blood altered the field, not their bodies, so that it kept them alive.
If they had to give someone Jack's imortal powers, i would rather it have been the girl. Rex was too annoying start to finish. My guess is the point of a 'next season' is that Rex is somehow the new key since jacks ability transfered and he'll have to sacrifice it to end the next threat from 'plan b'. Though i'll be surprised if starz reups it.
