From Wikipedia: Qui-Gon was supposed to make an appearance in Star Wars Episode III: Revenge of the Sith (2005) as a Force Ghost, and Neeson had hinted at involvement.However, he was ultimately unable to appear due to a motorcycle injury, and his character is only mentioned in the film. I hope that in a future release of the movie they will go back and put Qui-gon in a scene with Yoda.
I believe the ROTS Gameboy game features Liam's dialogue ( in text form, obviously). Sent from my HTC One X using Tapatalk 2
Found this deleted scene on youtube, but it uses someone else's voice. The uploader says it was included as a deleted scene on the blu-ray. I would have liked to see Qui-gon talking about Anakin, or commenting on the young skywalkers.
Yeah, I wouldn't mind seeing it in a future release. The scene didn't get finished to begin with, so they had to work with what they had.