My own concern about this is that the loss of interest in diplomatic or international history is likely to result in a lack of the expertise needed to conduct diplomacy. My experience was that diplomacy really is directed by the man (or woman) at the top. As I move up in the State Department (not particularly high), I found that the higher I went, the more likely it was that senior people would take an interest in, and control over, the issues I was working on. In fact, often the issues would be decided by the White House, not just by the Secretary of State. Historians might resent that the system works this way, but denying that it does is likely to result in an unrealistic understanding of history.
I was just listening to Obama talk about health care, and he repeated a line I've heard before when people complain about all the things he is involved in, such as the auto industry, he said he would rather not be involved in these issues, because he already has so much on his plate, and then every issue he mentioned was a foreign policy issue -- North Korea, Iran, Iraq, Afghanistan.