lol thats really poor wording. Even if he isnt dead, they should still say it because thats how it was portrayed and supposed to be seen as.
As for 8 seasons, I guess that means they felt they can't finish this story in two more seasons as 7 was the number talked about the last couple years. That's fine by me as long as it doesnt dilute the story, but I doubt it considering how much has been left out so far.
A prequal type of show might be really cool. There was always talk amongst fans about doing a Robert's Rebeliion show, but GRRM said that would be pointless because by the end of the series we will know how that truly went down anyway. But it would be cool to see those actors again. Either way, there's plenty of other backstory in the world that they could use or create.