In my opinion Hagrid has played a huge role in the book so far. But I think he must even a bigger in the upcoming books. I posted in the theories section that I belive Hagrid to be the Half Blood Prince. I have many reasons why I think he the HBP and/or why he is so important.
Firstly, Dumbledore tursts Hagrid a LOT.
Secondly, Dumbledore let him stay at Hogwarts even after expulsion. So he must be important to the story.
So that being said. What do you think Hagrid's future in the series will be?