Size and Setting
The map of the Chaos Scar doesn't come with a scale and even the details in the adventures tend to give conflicting information about the size of the Scar. On top of that is the placement of the Chaos Scar within the Nentir Vale in later 4th edition products. If you go with the placement in the Vale, the Chaos Scar is about 5 miles long or about 500 feet per square. The hints in the adventures indicate it the scale is more like 1/2 to 1 mile per square which really makes it too big to place in the Nentir Vale.
My assumption is 1 mile per square in order to give room for exploration and plenty of space for all the baddies in the Scar. Since this makes it too big for the Nentir Vale, I've placed it no place in particular except that the town of Wellspring is about two day's travel away, the Quarter Moon Inn is halfway between the Keep and Wellspring and Dardun is also within a day of the Scar.
Obviously there are different ways to do it; these choices have been made to create a certain type of game.
Future Adventures
The Chaos Scar is only meant for Heroic tier adventures but I felt that there were three more adventures that fit the feel nicely with their focus on start-touched themes. "Touch of Madness" from Dungeon #161, "Depths of Madness" from Dungeon #162 and "Brink of Madness" from Dungeon #163 for levels 10,11 and 12 respectively. This is why the town of Wellspring is included as part of the setting. Also including Stormcrow Tor ties them even closer together.
Beyond this I can't think of any pre-made adventures that would naturally flow so the rest would have to be homemade or in a different direction. Usually by this point in a campaign the adventures are writing themselves, however. If you want to get epic, have more stars begin falling from the skies all over as part of an invasion...
