Most times there are easy questions, some times they are hard, and once in a while we have subtle issues that are argued by those who know something about the law; but rarely do we have easy questions that are hard.
To start, I don't have the answer. The sad part is, this is kinda what I do. I can argue principles if I like. However, I suspect there is some guidance in rulings or cases out there. Sorry, I just got home from 11 hours of doing such things and don't really want to do any research right now. If you don't get a good answer from the other knowledgeable people here or from some who are expert on looking things up, "bump" this after tax season. I find the question interesting. (By "bump" I mean you post to the thread again to bring it to New Posts. If you get more information, even the better.)
As to principles, the basis of things is as of the death of the deceased. Even if he died in England. (I assume you are in the U.S. If not, move on sir, we've got nothing for you.) I also know people who have "invested" in Iraqi currency (Suitcase full of bills. It is quite impressive.) Tried to sell them and took a loss. It is a valid loss as currency speculation is big money for some. Winners pay tax, losers take a loss. Yet, an undistributed inheritance? I have not seen that. Even if it was distributed, it does not change the basic question too much. Is the question intent? Is the question reality? Is the question control (when combined with reality and intent)? I don't know. Without research, I could argue either side.
Wait for someone knowledgeable in international issues or who are good at looking things up. If you don't get a good answer, bump. I might just try.