If the U.S. starts witnessing person-to-person transmission beyond the Dallas health care workers and those with whom they had contact, then he will almost certainly be replaced at some point.
I'm not sure about the exact reasons such a team wasn't sent. However, I suspect that it is part of a larger problem that has plagued the U.S. government in recent years: a lack of strategy for such circumstances on account of a lack of contingency planning. While this problem doesn't garner the headlines the seemingly endless Republican-Democratic clashes receive, it is a significant problem that has hobbled U.S. domestic, foreign, and military policy, leaving the U.S. behind the curve of events and having to scramble to catch up. IMO, President Obama (and if he doesn't, his successor) should create a crisis working group containing such people as the Secretary of State, National Security Adviser, Secretary of Defense, etc. That group would be charged with identifying the major risks the U.S. could confront within the next 10 years. Afterward, each of the major departments would be charged with developing a strategy for such events and scenarios that could arise.
Even if one might not have expected Ebola to move into the U.S., the threat of a possible viral outbreak (be it from natural or manmade origins e.g., a biological weapons attack) has been in the mix of widely discussed possibilities. Logical "what if" questions would concern the type of pathogen: anthrax (used in the past), small pox (rumored), bio-engineered influenza, etc., tropical diseases (often brought up in the climate change debate), each of which would require a response.
The same holds true for foreign policy. With respect to Syria, the risks associated with a decaying authoritarian regime were not novel. One has witnessed the consequences of such decay in post-Tito Yugoslavia, post-Assad Iraq, Lebanon, etc. Syria is, as U.S. Ambassador to Syria Richard Murphy put it in 1976, "a patchwork quilt of small groups." Moreover, these groups have had major differences. At the same time, there were also radical Islamist elements devoted to toppling any kind of secular order present. Syria was a proverbial powder keg. Yet, when the protest movement was shoved aside by armed elements, the U.S. naively assumed that the democratic protest movement (almost certainly a minority among the overall population) had transitioned into armed democratic uprising. Notable former U.S. statesmen ranging from Brent Scowcroft to Henry Kissinger urged extreme caution in making such a diagnosis. As Kissinger later noted in his World Order, among those who took up arms, "few elements...could be described as democratic, much less moderate." Yet, U.S. policy was based on the false assumption of a democratic and moderate uprising. Rather than merely condemning the Assad dictatorship for its brutality, the U.S. boxed itself into a strategic lockbox by calling for regime change. Now it has less strategic flexibility than might otherwise have been the case, even as the deepening power vacuum was filled by the increasingly extreme elements such as ISIS.
There are differences between the nurses union's account and what the hospital has said. The matter needs to be examined.
Given his public role on CNN, I suspect the position of Surgeon General might be a better fit for him. I'm not sure that Dr. Gupta has the management experience to run a large entity like CDC. The CEO or COO of a leading hospital or medical research institution would probably be better prepared to run the CDC.