Do you think that we will ever see it in this lifetime?
Jane Jensen has already started work on/finished a few different games after GK3. I'm hoping that after she gets her game design company started up and running that she will be able to dedicate time and money to developing GK4.
IN GK3 it was hinted that GK4 would be about ghosts. Jane Jensen is one of the best game designers/writers I've known, I'm really looking forward to seeing what she comes up with.