After the blitzkrieg in Syria, the Sunni "jihadists" may not stop, and quite possibly will not stop. Appetite comes with eating, and rapid victorious campaigns very often become in history a prelude to new successful conquests.
This is exactly what happened with the Arabs themselves when, with extraordinary speed they captured Baghdad and Damascus and rushed in all directions: from Byzantium in the west to Iran, the Caucasus and Central Asia in the east and Egypt and North Africa in the south.