Flying Blue elite-level members can now carry over any extra Level Miles (elite-qualifying miles) earned into the following year. Every Level Mile earned above what elite members need to maintain their current level will now be saved and automatically transferred to the Level Miles balance for the following year. You must take at least one paid flight with a SkyTeam member airline that qualifies to earn Level Miles during the membership year to retain your status earned through rollover miles.
Bottom line: Delta SkyMiles also allows extra elite qualifying miles to be rolled over to the next year. The thought behind the offer is to keep members from switching allegiance to another airline once they earn elite status in their primary airline.