Game of Thrones actors are typically pretty good about keeping the show's secrets away from fans until they're revealed on screen, but they're only human. Sometimes an innocent question can lead to something like Sophie Turner accidentally leaking a release date for the final season, or even Iain Glen potentially letting it slip that Ser Jorah Mormont will apparently survive the war in Westeros long enough to be around for the show's series finale. The latter potential revelation happened recently when Glen shared his excitement over the show's ending. When asked if it provides closure, he said:
Yes, I hope. I can't tell, but I am one of the few people who has read the script and I know the ending and what happens. When I read it, I thought it was rather brilliant. I am a bit of a fan of the series as well, and it satiated my expectation and hopes, I felt (it was the) conclusion. . . . But we will just have to see. You know with something this big like Game of Thrones, you cannot please everyone.
Super-secretive television shows don't just hand out series finale scripts to cast members who won't play some part in the episode, so it sounds as though Ser Jorah Mormont will indeed be around for the Game of Thrones finale. That's not all that hard to imagine, considering Jorah already survived contracting greyscale, so what's a White Walker apocalypse after conquering that? Jokes aside, Jorah is obviously well-known for his strength and training as a fighter, so it may not necessarily even be a big spoiler to learn he'll stay alive long enough to close things out, provided the script-based assumption is true.
That said, there's some reason to doubt that Iain Glen is in the Game of Thrones finale, despite having read the script for it. Fans may remember that some members of the cast and crew were gathered for a marathon table reading of the final season not that long ago, and while we only know of a few people who were for sure there, Iain Glen could've also been present. In any case, it was revealed many actors in that room learned of their character deaths prior to the end of that table read, and while not everyone may have stuck around for the very end, Glen specifically noted to Indian Express he's a fan of the show. So wouldn't any real fan of the show stick around to see what happens, regardless of whether or not their character was still in the picture? Especially if they had permission.
Additionally, HBO recently implied fans should expect a lot of characters dying in Season 8 of Game of Thrones. Jorah Mormont is a strong fighter, but with the relevant cast in the series set to drastically be whittled down, he seems like someone who would be killed off quicker than most. Then again, Game of Thrones usually goes for quality over quantity when it comes to jarring character deaths, so perhaps Jorah will luck out due to his death not necessarily riling the fanbase up as much as some of the others that are still breathing.