If Admiral Harward comes in as the new NSA, we'll have General Mattis as SECDEF, his former CENTCOM #2 as NSA, and his former assistant division commander as Secretary of Homeland Security. This is a hardened team that knows how to work together from more than a decade's wartime experience.
There is a question about what will remain of the President's foreign policy agenda. Whatever else may be said about Trump, good and bad, he was not elected to continue inherited policies. On the other hand, it may be that the American people do not mostly care about foreign policy, and just want steady hands to keep that locked down so they can worry about the issues they do care about -- chiefly, among Trump supporters, immigration and domestic economic growth. (Immigration is often said to be a subset of 'domestic economic growth,' even, as one of the concerns about it is the degree to which it is suppressing domestic workers' wage growth. However, I suspect that the rapid and uncontrolled immigration of the last three decades has created immigration as a substantial issue in its own right -- relieving pressure and buying time for assimilation strike me as things people care about independently of economic consequences.)
The Secretary of State is still on board with a new foreign policy, and officially he is the chief of the President's officers in this regard. Still, the military and security aspects of the state have long since outgrown its weak diplomatic arm. As professionals, all these career Marines and Sailors will have the utmost respect for civilian control of the process. Still, there is going to be a weight on their side of the scale that even mindful respect of State's role won't be able to eliminate.
Of course, if you think Donald Trump's foreign policy ideas are no good, the idea of having seasoned military members in charge instead of the President and his Secretary of State must be attractive. They represent an apolitical, non-ideological, professional American government.
Nevertheless, I notice: "an apolitical, non-ideological, professional" government is exactly the opposite of what voters in both primaries demanded in 2016.