Incorrect.
You are making an explicit statement that certain historical trends and revisions of ethical systems are essentially inevitable. I am not twisting your positions into ones you don't hold and ascribing them to you, which is how the "straw man" fallacy functions.
Nor am I saying that "all predictions are impossible," rather that it is obvious that extenuating circumstances routinely disrupt what seems to be a "historic inevitability." Who predicted the assassination of Franz Ferdinand, and the world war that resulted? Who predicted the fall of the Berlin Wall? The rise of China as a quasi-capitalist powerhouse? The appearance of Al-Qaeda and international Islamist terrorism? The fall of Rome, the rise of Christianity, the appearance and spread of Islam?
On the flip side: In the 70s, Japan was regarded as a mortal threat to American industrial pre-eminence. The US economy subsequently boomed while Japan suffered from an extended deflationary cycle that still afflicts their economy. Or in ancient times, the divided Greek city-states seemed doomed in the face of Darius' overwhelming military might, yet the Persians were driven out of Greece in the end. And surely, many empires presumed they would "inevitably" persist far longer than they actually did.
Trust me, we could sit here all day and rattle off failed predictions and massive surprises throughout recorded history.
History is usually only "predictable" in hindsight.
True. However, my examples are nowhere near as extreme or outlandish, and numerous examples are drawn from history.
See,
that is a straw man argument.
I am not stating that the US is
going to turn into a totalitarian state. My point is that because you cannot predict the future, it is impossible to establish ethical guidelines based upon presumptions about the moral guidelines that will be established by a future society.
The evidence is abundant that history is not predictable, nor are social attitudes.
More importantly, if you index your ethical premises to an unknown future date, what are the ethical premises that the Future People will bring to bear? Won't they in turn be obligated to guess what morals the Future Future People will hold? How long in the future should we look -- 50 years, 100 years, 200 years? The very idea either turns into an infinite regress or a series of moving targets, each less predictable than the last.
Last but not least, why should I care about a future judgment? I'll be dead and buried by the time such an era rolls around. Do I really need to concern myself with being judged by people who don't yet exist, and whose moral principles are a huge question mark?
I recommend you stick with contemporary ethical principles, rather than grasp at an illusory future.