I believe Marriott has lots of unsold inventory it can add to the trust whenever it wants; it also has the ability to finish off units (e.g. Ko Olina) and add them to the trust to create additional points inventory to sell.
Do we know how much of the $900 million represents sale of points versus fees for enrollment of legacy weeks?
My own theory is that Marriott is buying units opportunistically, especially when the units are in locations where the trust owns little inventory (such as Desert Springs Villas, Mountainside, Waiohai). Marriott needs trust inventory at these locations to fulfill requests by trust point owners to reserve weeks at those locations.
The 900mm is my estimate of new contract sales since June 2010. It is an average of 600mm/yr run rate. It is not exact, but close enough.
As of September 2011 Marriott placed the future contract value of completed North American inventory at ~840mm. So, ~690mm of built inventory remaining, total (a little over a year of new contract sales).
An est. $125mm in completion costs will bring another 900mm in future new contract value, if sold at retail. Or, part or all could be bulk sold as previously stated an intention of doing.
I agree that Marriott will acquire existing weeks opportunistically to fill holes in exchange inventory. But, new contract sales will consume all it's completed inventory within the next year or so.