I think it's almost been proven that there will be a Scouring of the Shire quest because:
1) all of the quests are named after chapters in the books
2) the only reason Scouring would be left out is to make Mount Doom the climactic endinh
3) Mount Doom is the third chapter in book 6, so
4) If Mount Doom was the end, the 3 quests would be The Tower of Cirith Ungol, The Land of Shadow, and Mount Doom
5) we just got a saga box announced called The Land of Shadow, and
6) the designers probably wouldn't make a quest in one box that has the same title as a completely different box, which means
7) they could not stop at Mount Doom if they wanted 3 quests in the box
8) the quests are The Tower of Cirith Ungol, Mount Doom, and The Scouring of the Shire