He added: "Two hours per episode seems like it would be excessive, but it's a great show, so who knows?"
Despite possibly being feature length, he insisted they would remain at home on HBO, and would not premiere in IMAX as was previously rumored.
Bloys also discussed that the prequel spin-off currently being developed would not air for "at least a year" after Game Of Thrones concluded.
"The No. 1 priority in all of this is the final season of Game of Thrones. I don't want to do anything with a spin-off or anything that detracts or distracts from that," he said.
"That season will happen, and my guess is it would be at least a year before you saw anything else.
"What I don't want is the attention to be drawn from the final season, which I think is going to be epic and amazing, and somehow have the distraction of a new Game of Thrones airing right after that. It's best to separate it and that's what we'll do."
While the scripts are written for the final season, it has no set air date yet.
HBO is in fact working on four prequel spin-offs with the help of George R R Martin, the author of the Song Of Ice And Fire series the show is based on.
Game Of Thrones showrunners DB Weiss and David Benioff however will walk away to focus on a new HBO drama, Confederate.