Ex-Factor

See what I did there?
Britney's leaving the X-Factor, there's no question about that. Why or how is where the question lies. Did she walk away or did X-Factor tell her to watch out for the doorknob on the way out?
The idea of a mutual dissolving of the relationship is a joke. Someone said see you later first. Relationships never mutually end. It has to start somewhere. In this case, either Britney said to X-Factor, thanks but no thanks, or X-Factor said to Britney, your services are no longer required.
The first rumor to come out was that X-Factor would not ask Britney back for another season. Then, the rumor changed to Britney was quitting the show. What's right and what's wrong?
Some people want to believe that both parties got together and decided to go their separate ways. That's a highly unlikely scenario. What's more likely is that either low ratings scared X-Factor into deciding to move on or Britney was afraid X-Factor would dump her and chose to go on the offensive.
Whichever scenario is correct, someone is gonna look bad. If X-Factor tosses Britney aside, it makes her look less important. If Britney walks, it makes X-Factor look less important. You always want to leave a situation; you never want people to think you were removed. That's why you'd quit a job before you let your boss fire you.
It makes more sense that Britney got her walking papers (or, more specifically, didn't get any papers), then to think she chose to leave. At one point during the show, she said when asked if she'd return, "Yes, definitely." Later on, she changed her story to, "I have to think about it." But you can imagine her change of heart was more for negotiation sake (and probably at the request of her management team).
X-Factor, on the other hand, paid $15M for Britney, got marginal ratings, and was left in the end with three choices. Of those three, were they going to bring her back at the same price, give her a raise or let her go? There was no chance of her getting a raise, since the ratings for her season were lower than season 1. They could have offered her another $15M, but that's a lot of money to pay someone to judge the third most watched singing show on TV.
Really, they had one option (because offering her less money would have been a slap in the face, especially since she was quite competent at her job (and at times the only reason to watch)). Unless the ratings trended upward from episode one to the finale (and they didn't) they had to let her go.
For Britney's part, she had to get it out there that she CHOSE to leave to focus on music so she wouldn't look weak. J. Lo did the same thing when she left Idol. And it seems people are buying it.
I'm sure she and Fox will come to terms on some sort of mutual press release where both parties look good. They'll all say they agreed to part ways. Fox will miss Britney. Britney will miss the show. Yada, yada, yada. No one has released an official statement yet, but you can expect one to be forthcoming soon.
I enjoyed Britney's time on the X-Factor, but am of two minds about her inevitable departure. I'll miss seeing her twice a week for four months. Then again, I won't miss watching another singing show.
I'm sure once she's officially gone, writers will have a good time penning stories about how she was a massive disappointment, a waste of $15M, etc., etc. I don't know if that's really fair, though, since it's quite difficult to crush something on your first try.
If anything good came from this, it was the fact that Britney proved the doubters wrong. They said she'd be a trainwreck, yet she was composed and professional. However, the doubters claimed victory by calling Britney a boring judge, which to them is akin to being a trainwreck because both mean failure. In fact, many critics and doubters, after the fact, wished it had been a trainwreck (of course, had it been, they'd have claimed victory; though, they still claim it, even though she wasn't a mess at all, meaning Britney was in a no-win situation).
Years from now, we'll look back at Britney's X-Factor run the same way we do with Ellen DeGeneres on Idol. It happened, we saw it, but it ended up being pretty meaningless in the long run. Britney hasn't built a new career for herself as a TV judge. Probably for the best, since her original career is far from over.