The return of the wizened sage has been all but confirmed by Star Wars 8 director Rian Johnson. Lucasfilm confirmed some time ago that actress Lupita Nyong'o would be a returning cast member in the upcoming eighth instalment in the franchise. However it was unclear in what capacity she would be back. It was speculated that this was a speaking part only, perhaps as part of a flashback scene. There is precedent for this in the new trilogy as Ewan McGregor did some voice work on Star Wars 7 despite the character of Obi-Wan not being involved...or alive.
Rian Johnson recently dropped a massive hint, essentially confirming that Maz Kanata is properly back in the next episode. Johnson posted this image on his Tumblr account recently of the filming of episode 8.
The image appears to of the motion capture filming of Maz Kanata. It is unclear whether or not the person in the suit is actually Nyong'o but it undoubtedly is. It will be great to see Maz return in the next instalment as she was one of the most fascinating new characters. Being so ancient, she has been around for a lot of the major events in the Star Wars universe, basically the new Yoda. We will see Kanata again, along with Adam Driver's Kylo Ren, Daisy Ridley's Rey and Boyega's Finn in December 2017.