It is possible that the show will thrive without him, but consider the odds. Shows don’t last long without their foundation. How far did The West Wing go after writer Aaron Sorkin left at the end of Season 5? How good was The Office when its star Steve Carell left at the end of Season 7?
Also, the episode count has been cut down to 10 instead of the traditional 12. Alan Ball claims the decision was made to accommodate Anna Paquin’s pregnancy and for the “economics” of the show, but we don’t have enough fingers or toes to count the number of shows that have left the air after a shortened season.
On the flip side, the show’s consistent ratings and strong DVD sales could convince HBO to not stake the show after Season 6.