Authorship change on conference paper after conference program is printed
I have very little experience with "talk only" conference papers (and, as jakebeal correctly asks, why is it a paper if there is no paper?), but generally, the ordering of authors (or even who is an author) of a conference submission has very little to do with who prepares the presentation or who actually does the talk.

Rather, the order on papers is usually either alphabetical or by some measure of "who did the most work" for the actual research that is being presented. Hence, a change in who presents a paper (which often happens, due to time constraints, visa problems, illness, ...) usually does not require a change in the order of authors, as the underlying work (and who did it) has not changed.