If you've played The Witcher 3, then you are probably aware of the occasion where Ciri describes, to Geralt, a world where she went to escape Eredin. She talks of a mysterious portal she went through with the help of Avallac'h.
Ciri describes the world as follows:
He found a portal and took us to a world where Eredin couldn't find us for... oh, perhaps half a year.
Geralt asks Ciri about the world and what was it like to which Ciri replies
You wouldn't believe me if I told you.
And upon Geralt insisting, she continues:
People there had metal in their heads, waged war from a distance, using things similar to megascopes. And there were no horses, everyone had their own flying ship instead.
This obviously suggests that she has been to a futuristic world where she witnessed something never seen before. Waging war from a distance using megascopes refers to guns and rifles. And, flying ships obviously means the flying cars which we have already seen in Cyberpunk 2077.
During a live stream, Youtuber "Parris", who has been given the chance to experience 4-5 hours of Cyberpunk 2077, was asked whether he encountered any Easter Eggs during his play,. He replied with a confident "yes" and explained that when following the Corporate life path, he came across a Witcher 3 easter egg. He ran into a magazine with a cover of Ciri on it in Arasaka Tower.
This begs a question of whether or not we will see Ciri as an easter egg in Cyberpunk 2077? All the evidence suggests that there is a high possibility that we might encounter her in the game as an easter egg, albeit briefly.
Considering her original dialogue with Geralt - she told him that she was in this "world" for perhaps half a year - it is likely she adapted her outfit and looks accordingly as well, before finally returning back to her own world.