The HBO Max library is expansive, including everything from original programming to popular films and series from the Warner Media library. As part of the latter, Gossip Girl will be streaming on HBO Max sometime in the near future, although a rep for the streaming site tells Refinery29 that there's no exact premiere date planned as of yet.
A press release for HBO Max said that Gossip Girl will be available "within the first year" of the site's launch. So expect it by May 2021 at the latest. For now, the series is still streaming on Netflix for those who need their GG needs satiated ASAP. The show likely needs to run out its Netflix contract before it will move over to HBO Max, which could happen anytime in the next few months to a year. So far HBO Max has only released their June 2020 schedule and Gossip Girl is not part of that slate.
It's possible that the series will start streaming on HBO Max this fall, in advance of what was supposed to be the premiere of the Gossip Girl reboot on the new streaming site. The new show takes place eight years after the original show ended with a whole new cast of teen characters — although Kristen Bell is reprising her role as narrator.
According to Vulture, the reboot was initially supposed to premiere in fall 2020 on HBO Max, but the current state of the world delayed production. "They hadn't even started production yet; they were in pre-production and ready to roll," HBO Max chief content officer Kevin Reilly told Vulture. There is no set date to return to filming at this point, but even if the series is able to get back into production as early as this summer, Vulture reported that HBO Max is now going to hold the premiere until 2021.
If the OG Gossip Girl series was going to hit HBO Max timed to that original fall reboot premiere, it's unlikely that will change even with the reboot's delay. HBO will want fans to come flooding to its streaming site when Gossip Girl leaves Netflix, whenever that may be. That would also give fans plenty of time to rewatch the six seasons ahead of the reboot release. Then, everyone can be primed and ready for new GG content to come in 2021.