I remember watching Blade Runner in 1982 and thinking "Nope! LA will NOT look like this on our world line in November of 2019"!And now it's 2019, the year of Blade Runner, and Akira, and others.
We should create a SFF Timelines thread to cover all the eventualities
Back in the 1950s when I was first reading science fiction with FTL interstellar flight most those stories were set 200, 300 sometimes 10,000 years in the future. It did not bother me one bit that I would not live long enough to see it.If you set a story in 4005, it may as well be 15005.
But stories set 40 or 50 years in the future always have the possibility of readers actually living that long.
Back when these stories were written, the idea of "in 40 years time but on a different timeline" was pretty meaningless.
Now it all seems perfectly reasonable, mainly because of the need to explain away continuity errors in Star Trek movies.
It is the scale of technology that becomes the factor. The basic engineering physics of the steam engine had been known since ancient times. It is interesting that when enough knowledge had accumulated it did not take a long time to evolve sophisticated steam engines.Whenever I ponder on what might seem impossible now but could perhaps be reality in N years time, I think back N years to the past and consider what people then might have speculated about today's world. 300 years is fine and dandy for FTL travel etc, given that 300 years ago we'd only just invented the steam engine, and cameras were still over a century from being invented.