Personally, I think it's ridiculous that Carrie fans think Sony is trying to make Miranda the next Carrie.
Miranda worked her way up for years before radio paid any attention to her, and she's always been known as a songwriter and not a vocalist.
There's really no comparisons to these two, other than the fact that they're both blonde Country singers, and honestly people make her out to be a much bigger threat than she is (or ever will be) to Carrie.
Carrie has been vocal about her support for Miranda for years now, and Miranda praises her constantly.
Both ladies have different styles, personalities and fans.
The label can do whatever they want with Miranda, but she's quite established herself and certainly doesn't need a boost from somebody else. She was selling Platinum albums and winning ATOY awards and having an impressive amount of success before she broke out. On top of that, she came in third on Nashville Star and still managed to steadily build a career, despite the slower climb.
Miranda, like Carrie, has had plenty of success, and I think it's unfair to suggest two artists cannot have fun together without someone speaking negatively of Miranda to build Carrie up.
There doesn't have to be a motive behind everything, and Miranda is no threat, but her own artist.