SoCal, I think you misread the OP. There is no talk of terminating the pension trust. They only want to terminate the inheritance trust.
Personally, I don't understand how the provisions of the inheritance trust call for a 12/31/2012 "scheduled" close date when the trust has an asset that will not be fully received by that point in time. If that is the case, however, the inheritance trust should have provisions in it that deal with what happens.
My guess is that the Trustee of the inheritance trust is already in a pickle because the inheritance trust should have closed and the provisions dealing with what happens with respect to amounts receivable by the inheritance trust after its close haven't been implemented properly.
I would expect the inheritance trust to say that any monies received after the close are treated as additional funds payable to the estate and subject to the will's provisions. This might be a far cry from 50/50.
The plan, on the other hand, has no reason to do anything other than pay the inheritance trust as long as it accepts payments. Once the representative of the inheritance trust tells the plan that the inheritance trust is no longer in existence, then the provisions of the plan kick in and no doubt call for distribution first to the spouse (if living), etc. If the provisions of the plan don't dovetail with the provisions of the inheritance trust it might be necessary to have somebody (like a spouse) disclaim in order to have them match up.
Everybody involved in the inheritance trust needs to be represented by counsel and the qualified plan should follow the instructions of the Trustee of the inheritance trust until it doesn't exist. After that, it must follow its own terms.
This is a complicated enough situation that the qualified plan should probably have its own attorney weigh in, as well.
Things can get very expensive when estate plans go awry. And having the inheritance trust "scheduled" to terminate before it receives the complete benefit from the qualified plan sounds to me like something has gone awry.