In 2014 it was announced that all previous Star Wars books, comics, video games, and other similar materials were to be moved under the Star Wars: Legends banner, leaving only the original six films, and the animated series Star Wars: The Clone Wars as the official canon. This effectively erased 37 years worth of material, including many fan-favorite characters and stories.
Some small parts of Legends have popped up in more recent official canon projects, most notably the return of fan-favorite character Thrawn.
Recently a fan on Twitter asked Leland Chee, a member of the Lucasfilm Story Group, if any more characters from Legends would be making their way back into official cannon. Chee responded, saying "You wouldn't believe some of the Legends characters that will be cropping up in various media in the coming months. Hey, if Tag & Bink can show up, ANYthing is possible."
Tag & Bink refer to characters from the four-issue Star Wars: Tag & Bink comic series who will be making an appearance in the upcoming Solo: A Star Wars Story.
While we weren't given specifics on exactly which characters will be reappearing in official canon, we at least know to be on the lookout in the near future.