The good news is that actress Maisie Williams has confirmed that April 2019 is the date we can look forward to. This was revealed during an interview with Metro (via Polygon) in which William was quoted as saying, “We wrap in December and we air our first episode in April . That’s a four-month turnaround for these huge episodes. There’s a lot that goes into the final edit. You would not want to rush this season at all. We owe it to our audience and our fans to really do this final season to the best of our abilities.”
We’re not sure if she spoke out of turn since no one has been able to confirm its release date yet, but given that she is part of the show (and has a huge role), we can only assume that what she said is correct. Season 8 will be the last season in the series and it will run shorter than the other seasons at 6 episodes.