At this stage, NASA should just funnel money to SpaceX as fast as they can, before the space programs of other countries make them an irrelevance.
Yes I know that's harsh, but how else can NASA sidestep the politicians that meddle with NASA's long-term plans every election cycle?
Well, nothing Musk has done so far is deep space-specific. In fact, the whole manned flight program comes from NASA money. Is he going to design the Mars lander, outpost, return vehicle and fund it all? I doubt it. So in practice it's going to be on the politicians' whim for quite some time still.