No, it was always the Teselecta. The Doctor himself was inside the Teselecta.
the Doctor was always a fake. His "death" is a cyclical time loop that goes on forever. His friends watch "him" get shot, burn the boat, and meet a younger Doctor at the diner. The younger Doctor then lives through Series 6 and goes to the lakeside, where River refuses to kill him and collapses time around them. The alternate timeline is undone, and River, now knowing that the Doctor is a fake, "kills" him and escapes. The older River, having already lived through the events herself, suggests that they burn the Doctor's body in order to destroy the evidence of it being staged, although she masks her reasoning by saying that they need to prevent people from getting their hands on Time Lord DNA. This is further evidenced by the fact that the events we see in "The Wedding of River Song" unfold exactly as they do in "The Impossible Astronaut", just as a stable time loop would, and by the post-Byzantium River (who we've already seen before in "The Time of Angels") who shows up later in the episode and says that she's known about Amy being her mother and the Doctor being alive all along, ever since Series 5. Since the events of "The Time of Angels" occur long after those of "The Wedding of River Song" and "The Impossible Astronaut", we know that River has and always will shoot a "fake" Doctor, because she's always remembered doing so.