The news that Arrow is ending in season 8 clears up some of the confusion caused by season 7's flashforwards, which revealed an unusual amount of details about the future of the show's main characters. There was a concern that the flashforward scenes that take place in Star City 2038 were not only giving too much away but limiting what the series could do with its characters as well.
The CW recently announced that Arrow is ending after season 8. With only 10 episodes airing in season 8, it stands to reason that Oliver Queen's story will wrap up either during 2019's Crisis on Infinite Earths crossover event or shortly thereafter, seeing as all the previous Arrowverse crossover events air during the eighth or ninth weeks of their respective seasons. What's interesting is that Arrow ending with season 8 actually explains why the writers and producers chose to tell Arrow's future already.
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As fans are aware, Arrow's first five seasons explored Oliver's story before he became the Hood (from the initial shipwreck to when he was finally rescued from Lian Yu), with season 6 featuring occasional flashbacks from various characters. Arrow season 7 shook things up by swapping out flashbacks with flashforwards. What was surprising about the flashforwards was how much the show was willing to reveal about the characters. In doing so, Arrow's flashforwards were spoiling the story. And now, with Arrow ending, it makes sense why.
Arrow's flashforwards did much more than simply telling the story of Oliver's son, William; they also introduced older versions of Rene, Zoe, Dinah, and Roy. Felicity hasn't appeared in the future timeline yet, but it's been stated that she's still alive. The inclusion of these characters is confirmation that they'll survive until the end of the series. This means that, despite Arrow's reputation for killing off key characters in past seasons, there's no need for fans to worry about what happens to Felicity, Roy, Rene, or Dinah.
Conversations between William and the other characters have revealed other details that will be adhered to for the rest of the series. For example, the flashforwards have revealed that Roy and William won't meet again until 2038, which means that the two can't share a scene at any point in the present day storyline.
However, most of these problems are erased by The CW's decision to end Arrow after season 8. Revealing too much would only be considered an issue if Arrow were to continue for multiple seasons. It would be problematic if revelations in season 7's flashforwards prevented the show from moving in a certain direction in a much later season. Since a total of only 18 episodes of Arrow remain, it seems feasible that the writers already know how every character's story ends, allowing them to carefully craft a story about their older selves and adult children.