I would also like to make the point of what do any of us mean by hub? Does hub mean equal to Chicago's present level of service and nothing less or just a major city's downtown station where 4+ routes intersect and a convenient enough connection can be made? If we are going by the first definition, then no, there is no way St Louis or any other city will be a hub anytime soon unless Amtrak expands service by several orders of magnitude. If we are going with the second definition of "hub" then it wouldn't take much to make almost any big city a "hub".
If we're talking demand, Amtrak has no way to divine internally demand for transportation even within its own system. Why would anyone consider Amtrak from Kansas City to New Orleans if there isn't a direct service? Or Chicago to Florida or anywhere to anywhere without direct train service? Amtrak's skeletal system is a network externality problem. People don't use it because it isn't useful therefore there is no justification for expanding the network. How and why we potentially get a more useful rail network in this country is irrelevant to me so long as we get one. And if telling Congress "Hey why are these major cities not hubs for the national rail network, cough up some cash for trains" gets us more trains, then that is a good thing.