If "A Song Of Ice and Fire" author George R. R. Martin doesn't finish his book series in time, will HBO be able to finish its hit adaptation "Game of Thrones?" And when exactly will Martin finish the next book in his highly popular medieval fantasy series?

Millions of fans around the world are anticipating the release of next book in the series, "The Winds of Winter," which is set to be released in December 2014, containing a reported whopping 91 chapters. Martin hopes to finish "The Winds of Winter" much faster than he did his fifth novel, "A Dance With Dragons," and HBO is encouraging him to "get writing."

"As far as I'm concerned, they can go on as long as there are stories to tell," HBO president Michael Lombardo told Entertainment Weekly during the network's press tour session in Beverly Hills. "We certainly haven't gotten anywhere near that conversation with [showrunners David Benioff and Dan Weiss]."

David Benioff and Dan Weiss are the main writers behind the acclaimed HBO television show. In order to adapt the lengthy novels into 10-episodes per season, they've split up the third book "A Storm Of Swords" into seasons three (first half) and four (second half). Season four will premiere next year, and casting has already been underway for new characters. Indira Varma has been cast as Ellaria Sand, and Pedro Pascal is set to play the fan favorite "Red Viper," Prince Oberyn Martell.

The cast has already been rumored to have begun filming for season four in Iceland, and producers have high expectations. "It's the toughest production schedule we've ever had," Benioff told Entertainment Weekly at Comic-Con recently. "We got more action, which is obviously more time consuming. It's a brutal shooting season ahead. But if we can make it through, yeah, I think it's going to surpass season three."

Show producers are relying on Martin to finish the source material in time, as Martin first started the series in 1996 and has yet to come close to completing it, with two more books left to go.

"I know there are issues with the books and catching up," Lombardo affirmed.

"Our line to George was 'keep writing,'" said HBO chief executive Richard Plepler.

"Yes. Get busy writing," Lombardo agreed.

For the Emmys this year, "Game of Thrones" has three of its cast members nominated, including Peter Dinklage (Tyrion Lannister) for Outstanding Supporting Actor, Emilia Clarke for Outstanding Supporting Actress (Daenerys Targaryen), and Diana Rigg (Olenna Tyrell) as Outstanding Guest Actress in a Drama, plus a show nomination for Best Outstanding Drama.