Eeehhh, that's not really true.
Early on, Rivera was willing to say definitively that it was Newton's job as soon as he was ready to come back. He hasn't been willing to say that since. In fact, he's been seen as deliberately vague on the issue.
Likewise, nobody was initially prepared to believe a quarterback controversy was possible. Now a lot of analysts believe it could happen, and others think it already is.
Granted, it still may end up playing out exactly as everybody believed it would in the beginning, but the discussion has definitely changed...a lot.
10-17 49ers, Allen has worst game out and first loss, sparking talks of bringing Newton back. This is all started by the pass rush which makes him give up the ball early in the game then making the Panthers to play from behind and abort the game planned run heavy O. Jimmy G gets 150 yards passing, his first game without an INT, Kittle goes for 100 and 1 TD.