Like Cold Fusion, or perpetual motion, some dreamer will change the rules.
Government will do anything to take control. Case in point. The Food and Drug Administration wants the authority to regulate supplements. This authority will expanded the agency's political power. Additionally, the agency acts to protect pharmaceutical companies, preserving the status quo. The companies do not want to compete with products of proven effectiveness, fewer or no side effects and lower costs.
Personally, I'm extremely sceptical of perpetual motion, highly sceptical of cold fusion, and pretty sceptical of the claims made by the supplements industry (although some supplements are plainly a good idea, there's just too little evidence for most of them, and far too many touted on the basis of reasoning like the "it's natural so it's good" fallacy or anecdote).
As for practical immortality. I doubt it happens. The mature technology may permit a person to live forever, but they won't. Life will see to it. People won't die in bed, except in rare circumstances. If I'm remembering correctly, some genius at an insurance company figured out a actuary table for an "immortal". I think the average was about 350 years, with a maximum life expectancy about 1000 years.
Now there's a fun appliance of stats. Even if you take out ageing, we do indeed remain very mortal indeed.
Various studies show that, when technologies make cars "safer", people tend to push the envelope further. (example: German taxis and antilock brakes) Might this principle apply if we push the boundaries of human longevity?
True that. My favourite example was the effect of making seatbelts in cars mandatory in the UK in the 80s. Deaths and injuries among drivers went down, even though people started driving a little faster; but deaths and injuries among pedestrians and cyclists went up, because the cars were moving faster.
Would more people engage in skydiving, racing powered vehicles ( including spaceships ), and other risky endeavors?
Tricky one, there. You aren't taking the risks out of those activities; if anything, you'd have more to lose if, say, you've got a couple hundred years of healthy life ahead of you than a few decades of physical decline. On the other hand, more people would be physically and mentally capable of various risky physical activities if we could eliminate osteoporosis, arthritis, Alzheimers etc.; so you might well have more 90-year-olds skiing, mountain climbing and so forth than we do today.
It would not surprise me to see many complex changes as a result of increased longevity. Over long periods of time, I suspect that many people would become fiercely resistant to tyranny. When you have the prospects of hundreds of years ahead of you, do you want your future to be limited by corrupt governments?
It'd be interesting to see just what might happen with immortality. There's a strong association between age and right wing economic views today, but also one between age and "don't rock the boat" political views. Also, continuing to hold views prevalent among the youth might last longer if physical youth is itself maintained longer, and the old are just that much older.