So 1980s was indeed confirmed by Kinberg/Singer. But I would say they should do just 1980. 7 years after DoFP. Obviously the younger cast isn't aging quite this fast in real life. So 36 year old Mcavoy/38 year old Fassbender being almost 50 is already gonna be a stretch. But also it leaves more room in the 80s and 90s to be explored in future sequels/inbetweenquels.
Don't agree. 1980 just won't work for this movie.
Think about it this way...
1. People want a young Jean Grey (new actress)
2. People want a young Scott Summers (new actor)
3. People want a young Ororo (new actress)
4. Some would like to see a young Nightcrawler (new actor)
5. Singer has indicated he wants Nightcrawler
6. Most people want Gambit
7. Singer has indicated he wants Gambit
So, let's start with the concept of having Jean, Scott and Ororo in the movie. The general ages of these characters are, at least to a degree, known. For example, we know that Jean was first visited in 1985 by Charles and Erik. Yes, that specific timeline is now retconned, but we can speculate as to when Jean was born based on that scene (her birthday is set because it happened orior to 1973).
I've speculated that she was around 15, while other indicated that she was somewhere around 11. The actress was 13 years old. So what we know is that she was somewhere in that area, between 11 and 15 (or so).
Let's split it for discussion purposes...
Going with 13 years old, if you were to try to have the movie in 1980 she would be 8 years old, and that would not make for a good character or a good movie.
What makes more sense is putting her age at 15 in 1985 and going with that year for movie. In a lot of ways it would make sense to show the scene where Charles (of course, not with Erik now) visiting the Grey household, but this time he doesn't put the mental guards in place and instead dedicates himself to helping her control her powers.
Now Scott might be a year or two older than Jean, and I believe Ororo is a year or so younger. In general the three are around the same age.
Now Nightcrawler is actually the easiest to determine, assuming that Mystique and Azazel are his parents. Azazel died in 1963 and First CLass happened in 1962. That means that he was conceived in either late 1962 or 1963. That would mean he was born in either 1963 or 1964. So in 1980 Nightcrawler would only be 16. If the movie was in 1985 then he would be around 20 or 21 years old.
And just for discussion, Gambit's age is also set and can be speculated on, based on Origins and such. My best guess is he is somewhere between early 20's and early 30's. And this seems to fit for Channing Tatum.
So, 1980 just doesn't seem to work, if the story is what most seem to want and what most seem to be expecting. My best recommendation is a movie that takes place around 1985...