In D&D 3.x, the core books stated that the default setting was Greyhawk and the first few adventures were set in it (e.g. The Sunless Citadel, Return to the Temple of Elemental Evil).
In D&D 4e, the core books stated that the default setting was Points of Light and the first few adventures were set in it (e.g. Keep on the Shadowfell, Pyramid of Shadows).
The D&D 5th Edition Starter Set includes a scenario called "Lost Mines of Phandelver" and the first adventures will be Hoard of the Dragon Queen and The Rise of Tiamat, all of which take place in Forgotten Realms. The core books haven't come out yet, but has there been an indication of whether Forgotten Realms will be the default setting for 5th Edition? Or have the creators indicated elsewhere that Forgotten Realms will not be the default setting, despite it being the setting of the initial adventures?