I think it's important to remember that a significant amount of the money in the partnership is Mr. Lampert's. In addition, much of the rest is long time clients (Dell, etc...) and most of it is family money, which is much more sticky that fund of fund or institutional money.
I have been told that they aren't completely closed, but my guess would be that if Mr. Lampert wanted to raise more capital he probably could. A run on the fund isn't out of the question, but I would think it's a lower probability.
And most lockups don't roll, however some do if you contribute new capital at a later date.