I find it somewhat disappointing to report that Entertainment Weekly has stated seven seasons is the end game for Game of Thrones. Conflicting reports have traveled around the web stating that 8 was a possibility as well, and while that was indeed mentioned as a possibility, it seems the writers and show runners think seven is the sweet spot.
“It was our unstated goal, because to start on a show and say your goal is seven seasons is the height of lunacy. Once we got to the point where we felt like we’re going to be able to tell this tale to its conclusion, that became [an even clearer] goal. Seven gods, seven kingdoms, seven seasons. It feels right to us.”
This, in my opinion, further solidifies speculation that a good deal of story on the Southern Kingdoms will be cut from the series at the interest of finishing out the story we are seeing. As of now the writers are saying they will work with George R.R. Martin to give the series the ending it needs, but I doubt he will give them the ending of his series when he still has two books to write. It appears the show and the books are set to have two drastically different endings, which isn't ideal, but at the rate the Stark children are maturing both sides are left with little option.