There is no secondary reserve currency the world can look to. The world is becoming increasingly hostile and unstable, and no one is in this position, or seems fit to serve this position, in the next twenty years. Its also the case that the US still has a goal of maintaining low inflation, and I think its likely we would pursue austerity on benefits before we would intentionally succumb to higher levels of inflation (as we already have).

Or, you grow the pie. Look to history to learn how empires of the past grew their pies.