And while that is quite the wait for timed exclusivity, there are still new story missions and plenty of other updates from now until then. Xbox owners are still getting the DLC, just not all of it at once. As far as I can tell the only mission missing from the expansion for Xbox owners is one of the Strikes. I'd say that's less than 15% of the total content (including weapons/armor, PvP maps, and other PvE content).