I think RCA is going to use the same method of promotion that they used for Kelly with Stronger last year. Single release first week in Sept, then the video shortly after and album in late October, early Nov. Christina should benefit even more because of The Voice promotion on top of everything else. Though, I expect she'll have to stick to NBC for all her promo opportunities because the other networks won't want to touch her due to the Voice and how the networks are so competitive in the Fall. But luckily The Voice is big enough that it shouldn't matter.
This has been up in the air for at least 4 months, people talking about the single, even articles from her Voice's mates but still no official release"s date.