Ray Machowski has now been confirmed as a returning character in GTA: Liberty City Stories. Ray, voiced by Robert Loggia, was a corrupt police officer working for the Yakuza gang in GTA3. He is best known for his paranoia.
Artwork released by Rockstar earlier in the year suggests that Ray will feature in Liberty City Stories, although nothing has ever been confirmed. Take2Games recently updated their main page with the same artwork shown under the filename "feature_LCS_mach.jpg":
Mach = Machowski, obviously. It's not exactly big news (and I'm sure it was fairly obvious) but nevertheless, worth mentioning. Stay tuned for more updates.