Right now, we only know that Bethesda plan on launching Nuka World, the next big story expansion for Fallout 4, and the last planned (so far!) post launch content for it, some time in August- the exact release date is unknown for now.
However, thanks to MrMattyPlays on YouTube, it appears that we may now have something more concrete than that- as he reports in the new video on his channel, it seems like Steam has recently ended up leaking the release date for the eagerly anticipated upcoming DLC- and its launch date appears to be August 30.
August 30 would be skirting the self imposed deadline of an August release that Bethesda have planed on themselves- at that point, it’s practically a September launch, and only very technically an August launch. So basically, it seems like you have far more than a month’s worth of wait ahead of you before you can play Nuka World. Hopefully it lives up to the wait.
As usual, take this report with a grain of salt until we hear more from Bethesda in the future.