I've recently binge watched all of the original Naruto series and have started on Naruto Shippuden (around episode 20 as of now). Recently, I heard that the movie The Last: Naruto the Movie came out. From what I have heard, the movie has spoilers about the end of the manga (like chapter 700), but I'm currently not reading the manga (though I plan on starting).
If I were to watch the movie, when does the movie take place within Naruto Shippuden, if at all? I saw somewhere saying that it took place at around episode 399-400, but I also heard that a series following Shippuden is coming, so I don't know if I should watch Shippuden, then the upcoming series, and then the movie.