I don't think it's ungrateful to expect new music from your favourite singer. I think if he had said officially that he has retired and he won't be making albums anymore, then we would all probably laugh... err..no, we would all probably accept it and take pleasure in listening to what we have. But because he hasn't said anything, we keep holding on.
Having said that though.... I don't recall any celebrity officially saying they're retiring, so I'm just talking shit really.