It was a comedy retro-future and not a serious prophecy to begin with. Yet we do have flatscreens, Google glass is coming, Kinnect will let you play games without using your hands ... "Internally" we must assume that the time-stream has been altered, perhaps by butterfly-effects emering from seemingly insignificant changes Marty and Doc effected in 1885. I recently added a little speculation to that effect to the "2015" page. Tirindo (talk) 19:14, January 7, 2014 (UTC)
Thanks for starting this thread. One thing that's somewhat of a surprise is that, although cellphones were around in 1989 when the filming took place, nobody envisioned that most people would carry a phone with them by 2015. It wasn't just them, however; most science fiction from the 20th century didn't envision the universal use of cellphones or the internet in the 21st. And I think that a 17-year old visitor from 1985 to our 2015 would probably be surprised at how many people seemed to be "talking to themselves", unaware that they were carrying on a conversation on a phone. McFord (talk) 16:33, July 31, 2015 (UTC)
"Examples must remain purely hypothetical, but one could for instance imagine that the great-grandmother and great-grandfather of the person who would invent anti-gravity devices in the 1990s met on a train in 1886. However, since the locomotive that would pull said train was stolen and destroyed by Marty and Doc already one year earlier, an entire family line faded from history. The inventor of anti-gravity devices was never born. Such hypothetical scenarios could explain why we are currently living in a 2015 without hoverboards and flying cars."
It's easier than that. The 2010 game established that Doc Brown himself, aged 17 at the time, invented the flying car, and the tech that makes it possible, in 1931. His prototype flew for a couple minutes and crashed spectacularly, getting him banned from the Hill Valley science expo for 50 years.
Upon arriving in 2015 for the first time and seeing flying cars, he may have applied the remembered tech and hover-converted the DeLorean himself (after all, getting a shop to do it was $40K). Some time after 1992 (the end of TAS), he decided to kick-start widespread use of the tech.
The reason why RL has no (practical) flying cars and hoverboards? We didn't have Doc Brown to invent the tech behind them in the first place.
Let's remember these two things:
1. Never think it's sad that October 21, 2015 is now the past. You can't have a present, past, or life anywhere without a future. Every day in time starts or started as the future.
2. We always still have a chance to make Back to the Future Part II get everything about what is still "the future" right. Once everything seen in the 2015 part of Back to the Future Part II becomes a reality, we should come up with a plan to show that. Cbsteffen (talk) 23:04, October 25, 2015 (UTC)